You guys are wrong with your description of Otaku. It means "(your) house", and implies that you are a hermit who refuses to go outside and only stays in with their stuff. It's an insult, and if you watch this you'll see that.
This is one of the best videos ever made when it comes to explaining "otaku". It's an anime classic, as well.
Although, for some reason the end of the H.264 version cuts off towards the last 4 or 5 minutes, which ruins a great scene.