Glad someone else mentioned gaming. For a while there I did watch Yogscast but generally I'm shocked at the popularity of gaming videos in general.
It seems that every almost new youtuber now wants to be a let's player.
Like anything, personality gets you far - so there are some likeable gamers on youtube but i'm just stunned by it's overall success. At the end of the day, some categories are so different that I don't really see myself as competing against them, they just bring more people to the platform. Let's hope there'll be some spillover into other genres.