Seems like the three creators in that post are using the "something reacts to" trademark, or something confusingly similar. Assuming the trademark is valid, I guess that's the right thing to do from the perspective of Fullscreen.
Looking up fair use is the wrong thing to do in that one video. Especially when he admits to having committed to copyright infringement of someone's music.
What's happening here is that people on YouTube are starting to feel the effects of the law that mainstream entertainment industry creators have had to deal with for a long time. Again, that's contingent on the trademarks being valid, which I don't think they all are. Let's see how the Ryan Morrison thing goes opposing them. It ain't cheap, though.
Also, I work with the lawyer who I believe was instrumental in getting the USPTO to reject Sony's Let's Play trademark the 2nd (and probably final) time. I helped write the blog post announcing it! So don't accuse me of being some kind of blanket corporate shill. I know some of you want to