A few times I’ve updated apps, but the App Store still says I have updates. So then I go to the App Store updates tab and there are no updates. When I exit the icon is gone, but soon it reappears.
Thanks for the response Mike. It was very clever and informative. I figured it was just a bug.
Are you accessing the App Store on your device or via your computer?
For iOS devices it is quite normal that you have to revisit the App Store to make the notification disappear.
The App Store is not multitasking enabled which means although your Apps are all downloaded and updated the App Store does not know it yet. As soon as you open it again it will recognize that your Apps are now up to date and remove the notification icon.
As for "reappearing" I can only guess that developers might be pushing out some more updates and fixes for the upcomming iOS 5 which Apple will announce on the WWDC at June 6. They probably want their Apps to be ready for it.