It's about the amount of personal information out there that we don't necessarily realize is out there. Of course this is stretching the truth but not by much.
Medical history can be hard to get, but one always has to be careful about the "consent to release of information" many people so casually sign off on. You might be surprised to find out who your insurance company shares info with. And by the same token, I see some of the medical info people share on social sites like Facebook, and it makes me shake my head to think how easy it is to mine data off those sites.