This isn't publicity, they're just easter eggs from the website to keep hype to a reasonable level without giving us real trailers. I agree with Mario_0, I think they're showing off the AI. As for the guy under the rock, I think it was meant to show how NPCs reacted to the guy, and how they walked by then stopped to take a look and gasp, then continued on.
I'm pretty sure the game won't be out for a good while yet. These are just little kryptic bits of info, not unsimilar to some sort of viral marketing. Infact it is, isn't it? The more hits the site gets, the more stuff is put on there. It requires the cooperation of communities to uncover the videos and reveal the game's mechanics.