There is this pretty cool research project at Stanford (it's headed by Andrew Ng of the Coursera fame) that uses NLP and machine learning to detect content that the user might prefer not to see. It's still pretty rough around the edges but this demo is pretty cool.
I actually really like that song, maybe because I came of age in the 80's. The funniest thing about it is that Rick Astley seems pissed. He should lighten up because nobody remembered anything about him before rick roll and now he's a household name.
This was from an interview a few years back. It could have been because he wasn't making any money from it. I haven't kept up, but glad he's embraced it.
Astley participated in a rickrolling himself, at the Macy's Thanksgiving parade a few years ago. He popped out of a float in the middle of another musical performance and started singing Never Gonna Give You Up. It was a staged stunt, with a canned background track ready to go, and the TV announcers obviously feigning surprise.
http://www.youtube.com/watch?v=dQw4w9WgXcQ