Yeah, you're going to have a tough time getting users to sign up for something like this, regardless of the approach. It might be a good idea to get involved with some online security research interest group since they may have some ideas on how to test this, if not be willing to help you run the experiments so long as you let them see the results.

> the same ISP may be blocking a site in one city but not another I can't say I've heard of this happening very often at all. How common is this? Or is this something you're trying to find out?