Hehe. You're correct, you're never 100% anonymous. But you're as anonymous (to us) right now as if you had a registered account. The only detail we can see about you is your IP address (which we have to be able to see, as does every website on earth or it can't send you data). Blame the TCP/IP protocol
To that end, we can see your IP as anonymous, or as a registered user. There's no difference.
The donation process is, to us, anonymous. We can't see any details about you, but PayPal would record your credit card number for the transaction. That said, the fuckers have suspended my paypal account this week anyway because apparently porn613.com carries 'unsavory content'.. so I don't even think we can get donations at the moment.
I'm pleased to see your comments though, they're much appreciated. Ultimately, denying users access to the site if they're not registered is absolutely not on the cards. The only debate (and it's coming from the users, not us) is to stop anonymous users posting images/comments. I can see their points, a lot of anonymous people post a lot of crap. There are, however, numerous that don't.
To be honest though, I don't really consider this my site. I try to make it not my place to make policy. This site belongs to its users, it's what they make it - be that a good place, or bad. We just try to provide an empty canvass for you all. We try VERY strongly not to have to police anything (the only things we remove are obvious spam and, on porn613 anything with minors or people who look like they are).