I am happy to see that the Picasa team launched their new facial tagging feature. I've had the pleasure of playing with it/testing it/providing feedback before its release and am glad to see it released to the world. While it was internal, I did not dedicate my time to seriously tagging photos. Consider: when something is in an internal testing phase, there's always an outside chance that the engineers might have to clear out historical data. Now that it's public, I've tagged thousands of faces.
I discovered something interesting from tagging this many faces. Let me give you some background: the facial tagging feature does two things very well: it can identify faces in a photograph, and it can identify when the same face appears in multiple locations. In other words, it can easily tell you when several photos contain the same person. What it can't do is tell you who those people are -- that's something you have to do. It may know that these are all the same person but only you know that's Chris's Mom.
So here's the thing. While looking at a nonstop stream of faces that represent my entire social graph, I all too often could not name face. Twice so far I failed to recall the name of colleagues I see every day. Often I see faces that I can only seem to tag as "Ellen's baby" or "Chris's Mom." You can get away with that sometimes but you can't get away with it when it's "your coworker who you mostly remember because of the great socks she wears."
This is unsettling. And it's also a good way to test my recall ability. You typically see faces in conjunction with other related faces. With Picasa, facial tagging lacks the context of related faces, and clusters of faces do not appear next to their related faces, so I find myself going from coworkers husband to niece's friend to next door neighbor. In this case, my brain cannot leverage its ability to cache related concepts up front.
Incidentally, what is Chris' mother's name?