I think it works pretty well. Granted, Metafilter is also heavily moderated to prevent conversation derails and general abuse, but that's also what the money pays for (not like money is a problem for TWTR, or is it?)

I don't believe the payment is used towards enforcing identity (MeFi values privacy and anonymity when needed) and locating abusers, but if things got really bad I don't see why that would be a huge problem.