If you keep pictures on your iPhone and you have your preferences set up so that every time you connect your iPhone to your computer iPhoto imports, you're going to have a problem. Every time you connect your iPhone, iPhoto is going to ask you if you want to import your pictures even if they have already been imported. For older version of iPhoto, there's not much to be done about this. But there is a fix in iPhoto '09. Just check the box next to "Hide photos already imported" and it will stop asking you if you want to import the photos that you have already imported.