The new face detection feature in iPhoto '09 is handy, but it's awfully buggy. It keeps trying to tell me that various non-faces are friends or family, suggesting them over and over again for everyone. Worse, the UI to untag these non-faces is unusably slow on my G5.
There's a simple workaround: name these non-faces as Not a face. That way, they stop showing up for other names, and as a bonus, you get a big pile of them that you can share for laughs, or put in your bug reports to Apple.
Likewise, iPhoto keeps showing me some of the same pictures of people I don't know at all. I name these Stranger, so they all end up together. If you later realize who someone in this group is, you can just rename them as needed.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090427151621786