Debaters Debating Debate

The Guardian's Charlie Brooker doesn't think that online debate has any value -and he compares comment-posting bloggers to mice on treadmills.
"...online quarrelling is also addictive, in precisely the same way Tetris is addictive. It appeals to the "lab rat" part of your brain; the annoying, irrepressible part that adores repetitive pointlessness and would gleefully make you pop bubblewrap till Doomsday if it ever got its way. "
We can think of a couple of online discussions that transcended "repetitive pointlessness," such as this one from Slashdot's Hall of Fame when Scientologists forced the site to take down copyrighted text, (the infamous "Fishman Affidavits") which turned into a lengthy commentary on online copyright. But Slashdot has its readers self-moderate comments and lets you set a threshhold under which you won't read the comment.
Have you ever had an online discussion that went beyond penis size and flame wars? What's the best (or worst) string of blog comments you remember? Was it moderated? And are we working out the most relevant questions of our time, or just playing idea Tetris?