Picasa facial recognition is freaking me out

I decided to play around with the 'People' feature on Picasa (Google's photo management software), and it's been eerily accurate (besides a couple of mistaken suggestions where it thought that my (male) friend was me, but since I've tagged him, there have been no further confusions).  All you have to do is name a person once and it will happily go through and find a major proportion of the pictures they are in.  The more often you confirm something the program is unsure about, the more accurate it gets.  I even tried tagging a picture of a friend where she is making this crazy expression, and just based on that the program has pulled out over 50 pictures of her, in all sorts of poses, good and bad lighting, weird expressions or not.  The only one it got wrong was actually her sister.

I'm both impressed and a little scared by the technology.  Not that I have a problem with it going through and finding all my friends, but I'd prefer to keep it local (that is, on my computer).  The default setting for the People feature is to synch with your address book, adding email addresses etc.  And you can't even delete an email address once it has been added (I chose to just change them to fake ones after I discovered this).  I love Google, but I don't want to give them detailed information about what all my friends look like.  Scary thing is, there's no way to prevent anyone else from doing this.  I can just imagine that sometime in the future (or even now) they'll be able to scan security footage or Google Earth images and be like 'Yes, we're 99.99998% sure that that's joeblogs@gmail.com. We know exactly how many times a week he goes to the supermarket/hairdresser/bookie/adult shop.'  

Note: I am taking some inspiration from the National Blog Posting Month (NaBloPoMo - and I hope never ever to say that out loud) people who are posting one post a day for a month, except that I now have four blogs, so will try to post one post a day over those four.  This one is gonna end up being the one with the random leftover stuff (not about life in China or about language), so apologies in advance.

Original post sent via email to Wendebulous