blocking spammers on twitter

[dninja at gmail.com (Robin Wood)]

Hi
I've just passed 100 followers on twitter, most are legit but I know
that some are spammers. Is it worth blocking the spammers or should I
just leave them?

I'm trying to work out what benefits a spammer can get by following
me, the obvious one is that I blindly follow him back and then receive
his spam, is there anything beyond that? Is there any indication that
one spammer will look at anothers list and follow the same people?

Really I supposed I'm trying to work out the twitter spam business model .

Robin