Have you ever considered getting a DNA test to find out more about your heritage? If you have, you might be thinking that it's private, and will simply give you a bit of information that will never affect anyone else. You'd be wrong.

DNA by its very nature tells people everything there is to know about your ancestors, and can quickly show that you are closely related to someone. Where's the harm in that? Well it depends on who knows.

Consider some of the most information-powerful companies on the planet: social networks. What if they had your DNA?

How Much Does Ancestry Already Know?

Okay, so it's clear that Ancestry knows all about people who are related to each other, by blood and marriage. There is anecdotal evidence in the system, right alongside scanned birth, death and marriage certificates from every country in the world. Professional historians and amateur genealogists tracing their own family trees have pieced together a vast database of people and their relationships to one another.

They also have an increasing amount of actual DNA to back up the connections they have in the database. They realize this is valuable data and Ancestry.com CEO Tim Sullivan says they are well on the way to providing their customers with health information from their records.

"We actually do think that health is a pretty natural extension of the core mission to help everyone discover, preserve and share their family history." Tim Sullivan.

In fact, the AncestryDNA database has over 800,000 records from around the world already. This number is rapidly reaching the 900,000 records boasted by 23AndMe, a company that specifically deals with genetic testing.

What Happens When One Company Knows Too Much?

It's actually a little unnerving to think about how much Ancestry already knows. But think on this: What if Facebook bought Ancestry? Think of all those long-dead relatives getting Facebook shadow profiles with DNA links to all the living descendants.

Imagine how upsetting it could be to get "You might know…" suggestions for the milkman you had as a kid. Think about how fun it would be to host a large family reunion with Facebook suggesting all your neighbor's kids should be invited.

If you're scoffing that this wouldn't happen, consider that 23AndMe is a company that is backed by Google. Google already knows just about everything there is to know about what you do, what you like, and who you're in contact with. It even has a social network most people have forgotten about.

And while Ancestry might not know who you chat to the most on a daily basis, once you get married and start having kids, they have a pretty good idea. You could say they're more of a long-term social network -- they just don't value your everyday social data as much as your life-changing events.

Law Enforcement Can Obtain Your Genetic Data

The cops really are interested in this genetic data, and if it's sitting around in a public database, you can be sure they'll be demanding access to it if there's a case to close -- and we all know there are plenty of cold cases lying around. So, expect your information will be searched.

Now, you might think that companies holding on to important medical information would have to abide by privacy laws like the HIPAA, but as they're just regular companies who do not always hold medical licenses, this isn't the case. That genetic information is currently considered in exactly the same way that your other social network data is -- and is handed over in much the same way. Perhaps as a society we should rethink this.

"Law Enforcement Purposes. Covered entities may disclose protected health information to law enforcement officials for law enforcement purposes under the following six circumstances, and subject to specified conditions: (1) as required by law (including court orders, court-ordered warrants, subpoenas) and administrative requests; (2) to identify or locate a suspect, fugitive, material witness, or missing person; (3) in response to a law enforcement official’s request for information about a victim or suspected victim of a crime; (4) to alert law enforcement of a person’s death, if the covered entity suspects that criminal activity caused the death; (5) when a covered entity believes that protected health information is evidence of a crime that occurred on its premises; and (6) by a covered health care provider in a medical emergency not occurring on its premises, when necessary to inform law enforcement about the commission and nature of a crime, the location of the crime or crime victims, and the perpetrator of the crime." -- HIPAA

If you've never committed a crime, you might not be worried about this. But, given that familial DNA leads to a lot of false positives, you might easily be called in for questioning in regards to something that had nothing to do with you. And aside from this being a scare, it could potentially ruin your reputation if the news got leaked, even if you did nothing wrong.

Familial DNA Could Expose Your Family Members

Don't forget that your genetic information is not just your own, as you share a lot in common with all of your blood relations. Once you've given your DNA for testing, you've inadvertently shared the private data of every person you're related to, whether you know them or not.

This means that they too might be considered a suspect in a crime they're innocent of, or worse as you'll see.

A Wealth of Knowledge For Your Doctor… And Your Insurer

These companies collecting DNA are doing so with supposedly useful purposes in mind, and one such purpose is that it will improve your medical history, and hence your treatment. All this information would be incredibly useful in the right hands.

Imagine if your doctor could easily see the genetic markers present in your family? What if they also could see what the death certificates of all your ancestors said? They could be on the lookout for certain diseases and give you preventative treatment in advance -- Great!

And if Facebook had the information, they would probably allow advertisers to use it, and you can bet pharmaceutical companies would target adverts on Facebook to you, suggesting you get tested for certain things or ask your doctor for a particular drug. This could actually be potentially useful, especially if you didn't know your family's medical history some reason.

Now, what if your medical insurer could see the same information? Would they be willing to insure you? If you were almost certainly going to end up suffering from a disease that required expensive treatment, probably not.

And what if your insurer knew that information because someone else in your family got a DNA test once? How would you feel about that? How will your great-great-grandchildren feel about that if it's you that gets tested?

Would your immediate family be affected if a genetic test proved (or disproved) paternality somewhere along the line? What if your grandfather could potentially be served targeted Facebook adverts for lawyers, suggesting that his kids weren't really his? If Facebook had the genetic information this would be quite normal.

Could You Get Genetic Analysis Anonymously?

As there are many great reasons for wanting to get your DNA analysed, some people might try to do so anonymously. But it won't actually keep you anonymous, as there are already too many ways to find out who the DNA belongs to.

Just think about it. For starters, you're most likely going to use a credit card to purchase the kit (23AndMe require you to use your own card deliberately), and you are sharing an awful lot of information in your credit card number, along with your name and address (easily obtained via your bank). You probably gave them your address when you asked them to post you the results, anyway.

Now, even just with the DNA test results, say you are quite clearly shown to be related to Ann, Mary and Bob who all live in the same town. It's not rocket science to work out the rest, as researchers have shown on multiple occasions.

With the wealth of social network information tied in with that data, you don't even need to be a sleuth. It's right there.

What Will Happen In The Future?

We can't honestly know how this genetic information will be used in the future, and yet we're doing nothing to protect public privacy. We certainly can't expect these databases to stay in the hands of the people who currently have them. Security threats aside, valuable databases are sold every day, sometimes just by buying the company outright.

Adding social media data to genetic data makes it all too easy for people to link our biological and social networks. Who knows what that will lead to?

Could you do this to your family? Have you already given your DNA without thinking through the possibilities? Tell us.