I'd guess under 100. If there's more than that it seems pretty obvious that they don't do anything except possibly get together once a week to swap "I hate america" jokes and get some baklava (every good club has to have free food at the meetings
). If there were even 100 people doing their best to wage a "war" against us, they're doing a pretty pathetic job.
(edit: The Iraqi insurgents are pretty bothersome, but I don't think most of them are Al Quaeda members. At least it's not terrorism in the same sense as 9/11 was.)