I think this will work out great for them. Somethingawful.com is one example of a site which has a pay-barrier to it's forums primarily for the reason to keeping out trolls. Now you may have mixed opinions over the nature of things discussed in the forums there, but the maturity of the discourse is pretty impressive for the size of the audience. The fact that so much of the topic matter is 'immature' only helps exemplify how effective the system is.
I hope you are joking. SomethingAwful is a troll-generating machine. They didn't make it premium to keep the troll out they made it premium to make it profitable.
Somethingawful has 100s of forums, all with wildly different rules. Some have virtually no rules, and are of course filled with trolls.
But of the forums meant for serious discussion, there is far less trolling than anywhere else on the internet. Not that many people are willing to pay $10 per troll comment- though they ban people very regularly.
There are forums and threads on SomethingAwful with fairly intelligent discourse. There are also threads and forums with "quality" trolling. Either way, the cost and the harsh moderation has definitely improved the quality of the site.
