Nope, I'm in several 18+ servers (most of which have nothing to do with FR, which makes this a bit more hilarious to me) and have been to a few porn websites now and then, never have I ever been asked any sort of identifying information. The most I get is "Are you over 18?" and a "Yes/No" button.

These people in the replies talking about porn sites that ask for credit card info?! What the hell sort of porn websites are these people visiting lol