Or how about the complete lack of privacy?

Let's be real, the government has a thing for overstepping its right to follow you around. Why turn every action on the net into a key, value pair that clearly identifies you, just to stop a few teenagers from crapping on a writer of novels for young people and a rock star?

Lower participation and, as a result, maybe lower advertising earnings. On the other hand, the cost of not controlling bad content could be much higher both in monetary and non-monetary terms.

Flipside, it could also mean higher advertising rates given the traffic is more qualified if the discussion doesn't degenerate into trolling behaviour.

Think about it, sites like 4chan have issues with getting advertisers BECAUSE of the extreme anonymity.

...Says Mr. Cosinepi :)