Though the level of discourse in YouTube comments will never win awards, Google appears to be quietly testing a comment search feature. You won’t find it anywhere obvious in the YouTube interface — not on a video page, not even in Advanced Search. It’s available at this URL (you can change the query at the end):
As ReadWriteWeb points out, this actually could be a valuable monitoring tool for companies, individuals, artists, and other celebrities that are the subject of a lot of YouTube videos and comments. There’s even a real-time element at work: Updates are pushed out as new comments are indexed, and YouTube lists a handful of “trending topics” from user comments.
But this appears to be very much a beta project. To test the comment search, I grabbed an exact snippet of text from a comment that was posted a week ago on one of my own videos. Comment search found no matching results:
Perhaps this is one reason why comment search isn’t yet part of the main YouTube interface.
Update: A YouTube product manager emailed this update regarding the comment above not appearing in comment search: “We return comment results from the past seven days and it looks like your U2 comment was just on the lip of that period.”