No, they just make you laugh.
All the 9/11 conspiracies are based on bad science and false assumptions. Yes, some hokey things went on, but hokey things are always going on. Pick any date and you can find examples of the government acting conspiratorially because that's their job.
Check out the myriad of debunkings of Loose Change, for instance:
http://www.thebestpageintheuniverse.net/c.cgi?u=911_morons
http://screwloosechange.blogspot.com/2006/...s-of-loose.html
http://www.pajiba.com/loose-change.htm
Then, just let Penn & Teller tell you how it is.