I've been mining a few coins for a while, including BTC, but I'm ready to actually buy some altcoins on an exchange, 'cause the price is right. I'm looking at Cryptsy, and to be honest, I'm a little reluctant to give my personal information to the site. It all seems legit, and I know many have done it before, but what is the purpose of needing things like photo ID and whatnot? Is that a US thing, or does pretty much every exchange want that information? And if they do... Why?

I believe for higher verification, some even want a Social Security Number? Why is that? Does anyone have more information regarding why they would collect that information? I don't necessarily doubt the honesty of Crypsy or any other big exchanges. But at the same time, I'm not going to run and give them information that they shouldn't have.

Thanks for any information you guys can give me.