Thread creation should be a moderator reviewed action. Sadly, this will never be the case.
That attitude is overplayed. Forums are self moderated, in that threads that are pointless can be ignored and they'll get buried and die. As long as the trash doesn't keep getting brought to the top it doesn't really matter that it shows up from time to time.
That being said, every topic has a chance at spurring a great discussion. Right now almost everything is hypothetical anyway, we really don't know a lot about Skyrim, but we're all really excited (some maybe worried) about it being released. Beyond that, the powers that be read things here and what discussion goes on here could influence the direction that is taken or help in some of the tough keep/drop feature decisions that will undoubtedly be made before the game is finished.
Long story short, if you find a thread to be worthless, simply ignore it and let it fall off the main page and die the sweet death it deserves. Posting in it to say it's a dumb thread only keeps alive longer and risks encouraging sub conversations about a threads worthiness to exist, thus prolonging it's death even further.