I didn't watch the entire YouTube clip, but certainly I'm right there with Misha in terms of sheer bafflement about Tumblr. It's oddly typical of fandom that it doesn't occur to these people that the daily dose of fandom happies they get from the site has in fact nothing to do with the site itself, just the community that's accumulated there (a community that may well migrate to the Next Big Shiny whenever it comes along.)