>>Of course, you still need to give a trial period of some length - maybe 30 days, something like that?
>
>The problem with a trial period is that there is no way to verify who the user really is. They can keep signing up for trial periods. Actually I guess there is one way, you can take a credit card... but this may deter people from even trying out the UT.

How about email address + name? It's not perfect, but a given user will exhaust a supply of easy possibilities before too many times :)