I used iPhoto for a long while as my one and only method of fetching and storing all the photos from my digital camera. Eventually I started dumping wallpapers in iPhoto too, and any miscellaneous image file I needed to save for any reasons. There are some good and bad things about using a program like iPhoto for data storage / organization. I think the bad probably outweigh the good.

A motto of Perl is "Make the easy things easy, and make the hard things possible". iPhoto fails, like so many other programs, because it makes the easy things easy, but it makes many hard things IMPOSSIBLE.