From that same thread, someone was downvotted to oblivion for saying Facebook would overtake Yahoo in 5 years. I think that prediction came true within 2 :-)

http://news.ycombinator.com/item?id=24616

Here's my own contribution to the downvoted-but-prescient competition:

http://news.ycombinator.com/item?id=488341

(It hasn't come to pass quite yet, but both Google and Facebook are destined to face antitrust scrutiny.)