I paid for 23andMe. I did it mostly out of curiosity, to see if there was anything in their genealogy report that would surprise me (there wasn't). I was also interested in their medical risk reports, although I admit to having very little knowledge about how reliable or extensive those reports are.

The thing is, I actually agree with all your concerns about privacy, but I guess I just disagree about the magnitude of the concerns. Of course there are risks of being targeted for ads, or treated differently by health insurance providers. I can't really justify my stance, but I guess I'm just less worried about the possible downside than I was interested about the possible upside.