Goldstone Rapper
Rediffusion PlayerofYear
You write something that parses the HTML to get what you want. YouTube's actually easier as they have an API so you can just call that to get all the comments for any given video.
Edit:
For example, all the comments for this video http://www.youtube.com/watch?v=X-p5g1bGuCU are available at https://gdata.youtube.com/feeds/api/videos/X-p5g1bGuCU/comments in handy-dandy XML for you to read into an app at your leisure.
Brilliant! Thanks for that. Very helpful indeed.