I'd heard the lawyers were already putting together a not-for-profit defense, I was thinking this might actually finally end up creating a test case for defining fan-creation bounds in terms of fair use.
Profit or lack thereof is irrelevant with regard to copyright infringement. Even if a fan film or a piece of fanfic never earns a cent, if it uses copyrighted elements without permission, then it is an infringing work. Consequently, the not-for-profit angle as a defense is a guaranteed loser, based on statutes and case law precedents. U.S. copyright law is not forgiving in the least.
Although I agree with this viewpoint, there are groups like the
OTW which make the argument that all fanfic is inherently transformative. (See the "Legal" section of the FAQ I just linked to.) Despite being started by lawyers and making this argument in a variety of venues, however, they haven't launched a test case themselves, so I would ideally like to see an on-point case about genre fanfic itself to definitively settle the issue in US case law.
^ I suspect that, in some cases, there is also a financial consideration: It simply isn't worth CBS's time to pursue every small-scale infringer; the legal costs would be prohibitive, and most of the parties are insufficiently capitalized to be able to pay damages.
That's what DMCA takedown notices are for. CBS could destroy the fan film community with a few dozen scary form letters. Fanfic would be a little more time consuming, but having an intern trawl the major repositories and send out a weekly DMCA request wouldn't be that expensive. I think there are even companies that specialize in that sort of thing.
Similarly, the OTW also launched their own archive of fanfic (with the motto "We own the ***damn servers!") that wouldn't automatically respond to DMCA notices. Having said that, I don't know how many they might've received since then or what their typical response is.