Easy now. Refuting a theory without solid proof is just as stupid as making one without any.
Except a new theory could be a right one. You never know.
Personnally, I wasn't in the World Trade Center. I wasn't in the planes, and I wasn't with Osama, nor with any member of the Bush family.
So I will only give my decision after leading some study on it, and I'd rather do it personally than on the internet.
The thing is, American administration could've organised it. And it served them right, uniting the country against an external enemy - always good when there are internal troubles (like, say, economic ones) - giving an excuse for invading oil producing countries - and around this dangerous one, Iran -, making lots of people enrole (thus decreasing unemployment), remembering everyone in the world who is the master and can blow your face if you stand against them and/or freedom, etc.
On the other hand, it could've been a real terrorist attack the US Government hadn't heard of. It would've also come in handy for the terrorists (I'm keeping it short because I don't have a clue about a terrorist's motives).
So, wait and see. One day, I'll take some time to find out. In between, there are just two theories.
PS : When you hear about something, don't try to remember who told it, from who he knows it etc. Just try to think and find who is gonna take the best out of this theory. In this case, this video looks true because the guys who made it wanted it to look so. I'm not saying it didn't happen the way they say it, just that you'll never be sure (and thus, you'll buy their next DVD).