I'd love to exploit ad networks user profiles for this. I.e., store some bits as "interests", by running a few appropriate google searches or hitting a few web

I'd love to exploit ad networks user profiles for this. I.e., store some bits as "interests", by running a few appropriate google searches or hitting a few web sites, read the bits by seeing what ads you're served. This would probably require a bit of learning and a redundant encoding to make it work, but...