[drlevy88]

Screen names, since I guess that is all you can count. Doesn't FR require uniqueness of email address, so that nobody else can sign up with a bannee's email addy?

[John Robinson]

We require a unique e-mail address per account. However, that is only to discourage abuse, to make it a little harder for the disruptor. It takes about five minutes to create a new e-mail identity if you know where to go.

As for the DUsrupters, I honestly don't know. In general, without respect to any particular place of origin, I think maybe several each day are banned just by the auto-ban filter alone. Then maybe that many again are spotted and put down by hand.