"Have you seen the video footage showing WTC7 going down? Take a look at http://www.wtc7.net/videos.html . It fell so straight down, it appears to be suddenly sinking into a hole."

Check out this site.
911myths.com

There are more plausible explanations as well as the various conspiracy theories listed here. When you can read all the theories and see the evidence for each, the idea of a conspirarcy seems more remote.