^^^Corporate legal departments are busy places, and sometimes they simply don't have the bandwidth to deal with every piddling little violation as it pops up. I work at a company with a lot of I.P. and our legal dept. makes note of intellectual property violations (in fact, one of our legal team approached me about this kind of thing just yesterday), even if they don't immediately act on it, but sooner or later they get enough of these on record to merit spending the time and energy to act on them, and when they do, a bunch of C&D (Cease & Desist) letters go out.
The more fan filmmakers push the boundaries of fundraising and the gray areas surrounding that, the greater the likelihood that CBS's lawyers will eventually say, "look, there's a growing trend of these groups using our I.P. to raise money," at which point, watch out.