David Cameron and his advisors are saying good 'ole Dave is on safe ground going on about Britain's broken society (he's been doing it for the last 5 years). They think the sort of speech he put out today will increase his popularity.
If the government want to increase their flagging popularity, pave the way for a limited U-turn on spending cuts to the Tories' favorite areas of expenditure (police, prisons), and deflect the public's attention away from the terrible state of the economy and the lack of growth that is likely to happen, wouldn't a countrywide set riots and looting be a good ploy? If everyone is focused on the riots, the Conservatives will be able to go on about Law and Order (traditionally one of their big themes), nobody will notice the economy going to heck in a hand-basket, and News International can fade into the background (Labour were getting good mileage out the phone hacking scandal).
So the riots look good for the government at the moment. Did they set them in motion? I doubt we will ever know.
(WARNING: Conspiracy Theory)