I just got this guy who registered in my forum 3 times in the role with the same IP. Can any user register an infinite amount of forum accounts with the same IP? If so, how can I restrict this or is it already restricted to 3 per IP address?

i think it's only checks for unique username & email (and not ip), but i could be wrong here - not 100% sure about that.

Edit: you can set "Allow Multiple Registrations Per User" to YES, and assuming he won't delete his cookies, he won't be able to register again. (under options -> user registeration options)

Shouldn't that be set it to NO? I think they're trying to avoid multiple registrations, not encourage them. Ay least that's the way I understood their question. I thought there was a hack that checked the IP at registrations? You didn't state your vB version number but maybe the hack was just for 3.5.

ooppps... i meant NO indeed, was typo.
thanks for this correction.