Not that I support the theory that it was a "controlled" demolition, but consider this.
First, there seems to be some kind of disconnect in how many floors it would take to "contolled demolish" in order to take down the towers. First, assuming the official story is correct, then obviously it doesn't take more than one floor being demolished to cause the "pancake" of the tower since that is what happened ... one floor gave way and the rest of them collapsed on top of it and that brought down the tower ... whether the collapse of one floor was caused by thermite, or a jet crash, the results should be the same ... so there is no need to have a theory where many many floors are rigged with thermite or C4 or whatever, all it takes is one (the strangest thing is that both truthers and ant-truthers seem to accept as fact that the whole building, or a good portion of it, would have to be rigged to demolish ... obviously that is not a correct "fact" as in reality the pancake effect disproves this theory .)
Now, we have to find a way for someone to get the necessary thermite onto one of these floors and rig the setup without being noticed and found out ... that would be quite a trick, except that according to the floor plans (released, if I recall correctly in the NIST report) in both towers, in among the floors that were hit by the jets, were large computer rooms ... the perfect place to set up some demolition equipment without drawing any undo attention.
Now, as I said, I'm not trying to suggest that the truthers have it right .. this is just "wild speculation on my part based on some known details of the 9/11 incident ... the computer rooms, which usually have large batteries for UPS purposes, shorting out and melting, could also be what was seen flowing down the side of the building and mistaken for thermite ...or maybe not ... but I think there at least are some unanswered questions that need answering.