Way back in the elder days of iPhone 3.0 Beta 5, there was some discussion on Twitter about how apps would have an incorrect icon, or would be missing an icon altogether. Since the iPhone 3.0 betas were private and not public, TiPb didn't post about it as that's just not how we play cricket. Private betas will have bugs, get those bugs reported, and hopefully have those bugs fixed by the time the software goes into general availability.
However, TUAW highlights that this particular bug is still biting iPhone 3.0, even in the release version. Now, as then, if you have an app that's missing an icon or has the incorrect icon, you can try to reboot your iPhone, delete the app and download or sync it back on, or wait for Apple to fix it in a 3.0.x update.
Meanwhile, you can let us know the funniest app mishaps iPhone 3.0 is giving you in the comments below.
(Mine is the little AIM dude swiping my 1Passwords Pro!)