There are, of course, some problems with the apparent independence of the 7/7 attacks - not problems frmo an investigative nature, but of a political consequence nature.
Firstly, if bombers are independent then all of a sudden that makes tracking them very difficult indeed. If people are spurred on by media broadcasts rather than, say, personal communication with terrorist agencies, training camps, etc, then tracing connections through network profiles (wiretaps, e-mail snooping, location-monitoring, etc) suddenly becomes next-to-useless.
But secondly, it swings the finger of blame around again. All of a sudden, "extremist terrorists" can no longer be blamed. The "home-grown" effect - British terrorists on British soil against British civilians - is twofold. One, the politicians will spin it as a "culture" of violence "infecting" our otherwise lovely society. But two (more importantly) there's that direct link between what the politicians are actually doing, and how people are reacting. In many ways, then, there's not much of a philosophical divide between all them people willing to march through London in disappointment at the ruling elite's plans, and all them people willing to blow themselves up. Reaction.
Hence why the ISC report focused on resources, not reasons - intelligence, rather than Iraq. The government have been found "clean" yet again, and all of this nastiness would have happened if we had or had not invaded foreign countries, despite what the terrorists say.
The upshot of this is, of course, tighter rein. More control over possible suspects (a definition which spreads even wider, now that it can't be predicted through social links), more ability to sort the guilty from the possibly guilty, and more propaganda to portray people with a bone to pick as an evil menace.
Perhaps the old British tradition of sitting down and having a nice cup of tea and a chat should be re-considered?