@Ted Clayton - "Update Notifier" does not seem to have been updated since 2010-9-20, but if it does not need to be updated, there would not be an update completed. However, I would expect them to alter the "Compatible up to:" if it works with the latest WordPress releases. If someone with the latest version of WordPress tried to install this plugin via WordPress, they would see a warning saying that it did not work with the version of WordPress they were using.

I honestly think that this is a huge challenge for WordPress as they seem to be targeting new or less experienced users. In my experience I would say that these users are the ones who have a higher tendency to be using outdated plugins.

Please let me know if you want statistics or examples and I will see what I can do.
Many thanks