I would guess that harming them or their families would not truly help anybody. I suspect this second lot are just a bunch of dickheads emulating & hanging on the back of the horrific events of 2 weeks ago.
My question is why are the security services not doing their jobs?? The emergency services on the streets are putting in some sterling efforts (as always) but they are always on the back-foot.
Oh & also...why do they hate us so much?? Maybe we ought to work on being more honest with other people in the world, the outspoken Ken Livingstone was spot on with what he said earlier this week.
Just my opinion... 
Chris, have you been reading the sodding Guardian again?
Firstly, it seems self evident that this is not just a bunch of dickhead opportunists. Where would such people get detonators from? No, clearly these brainwashed foot-soldiers have been well organised from above.
The security services have a very difficult, nay impossible longterm job. They are not allowed telephone encryption or phone tapping. Also you do not know how many attacks they have prevented and yet get no credit for. Your question should be better directed at HM Govt. If you've got any better ideas, then I'm sure Charles Clarke would be pleased to hear from you.
Finally, IMHO Livingstone is a total hypocritical tw at. He floods London with God knows who and then bleats when his great social experiment blows up in his (or more accurately, Londoner's) faces. His crocodile tears made me utterly sick last week. The reason the fundamentalists hate us is a combination of jealousy and frustration. It has bugger all to do with Iraq or Afghanistan(convenient excuse tho it is). No, it's to do with an inbred hatred of the West and all it stands for. These people hate our liberty, our lifestyles, our Godlessness, our wealth, our ingenuity, in short, our sucess. They base their lives on a literal interpretation of a 15th century credo and are frustrated when it proves incompatible with the modern world. So, without the Christian peoples all converting to Islam, there's probably little we can do other than keep our eyes peeled and report suspicious activity to the authorities.