how's that in web hosting?

Actually there is no need in sign up all of these sites. There are websites which provides free hosting. You can register if you want a website. But avoid giving true and personal information (address, true name etc) to those.

A lot of those e-mails could very well be spam. Anyone can send them. It is advised not to join a site that you've recived through e-mail, unless you know the sender and can reply back to them. Most sites like that use robot e-mails where they can send mail but you can't respond. There are a lot of ligit web hosting sites out there. You just have to take the time to do your research. And, no any real web-hosting service won't pay you to use their servers.... instead you'd end up paying them. And any honest to goodness hosting site won't e-mail you trying to get you to join. It can easily be a fishing scam designed to get you to fork over personal information. Don't fall for it.