By the way, the scammers on dating sites use a lot of paid accounts (and pay for them themselves most likely) considering they get a lot more money out of it and a paid account seems more legitimate. Just to say that making something paid does not necessarily remove all the abuse.
Worse, if the government keeps lowering the bar on qualification for shutdown, the margin for mistake will be so small that the best effort possible won't be good enough. There will be mistakes, fraud will slip through, and boom you're toast.
If the Feds keep going in this direction, at some point the risk of a free system will not outweigh the benefit. Before 2012 is over, there will be enough of these examples to start scaring the hell out of the average web service - if we're not there already.
Government enforcement of policies like this rely on scaring large numbers of operators through a small number of intense persecutions. It works unfortunately.
This matter is a mess all the way 'round.
One way to deter phishing forms, for example, is to charge enough for your service that it makes it very unlikely someone would use you for that. Jot mentions having taken down 65,000 phishing forms in the past year; charge $10 or $20 (or whatever, enough to wipe out the issue) upfront for each of those and that problem disappears instantly.
It's the difference between MegaUpload and DropBox fundamentally in how they deter piracy (or don't); applied to every web service.
Most of the time, when the government gets involved, the cost of a service or product skyrockets. They generate inflated costs either through monetization (eg education costs), or through regulation & compliance nightmares.
The government might just force a transition from the so called free web, to a nearly all paid services web. It would form a 'cost wall' that keeps a lot of the abuse users out.