RE: revenue generation for devs / pubs...
For every major game that he's covered and generated sales for, there's other games that people haven't bought but still got the majority of the experience for free by watching his videos. Is that fair to the devs / pubs who made those games? Don't you think they should at least be partially compensated by getting a share of the advertising revenue?
Again, genuine interest...
I personally don't feel that way. Hell, there was the Skate incident, where a game being glitchy and stupid was reason enough for so many people buy it after his videos, that it was reprinted years after release.
So I assume if people are willing to buy broken games just because his videos about them were funny, watching a good single player game won't make them less likely to buy it than they were before.
I've played Catherine quite a lot already, but I've been wanting to replay it for some time, and his recent playthrough didn't really help with that, actually, just made me want to play it even more.
But yeah, I guess it depends on how you personally feel about full playthroughs. The only cases where I even watch a full playthrough of a game I didn't play myself are cases where I'm very interested in the story but I have no plans to buy any of the platforms I can play it on. So they're not really losing a sale from me, I wouldn't buy it anyway. On the contrary, if I like it and maybe someday they port it to a platform I own, they might have a sale from someone who maybe wouldn't care anymore.