Yesterday, what remained of the Rolling Stones strutted carefully out on stage in Rio to an audience of over one million people.

That the Stones are still allowed on stage at all is a shining example of what the music journalist John Strausbaugh has dubbed "colostomy rock" - the continued weight exerted by baby boomers on what was previously thought of as youth culture.

The idea of the baby boomers is an essentially American invention, used to describe the unusually large cohort of babies born between 1946 and 1964 and swollen by a surge of postwar optimism.

Both British and American boomers are now hurtling through the demographic turnstile towards retirement, and the first of them will hit 60 this year.

Since they revolutionised every stage of life through which they have passed, say the pundits, they are set to upturn the business of growing old.

Because they refuse to relinquish the attributes of rebellious youth, the new middle-aged continue to crave the attentions of marketeers and advertisers. They also, apparently, wield huge political clout.

According to a report published by Age Concern earlier this month, it is boomers rather than the twenty-somethings coveted by David Cameron who are key to winning the next general election - and most of them haven't yet made their mind up yet how to vote.

Now, inevitably, comes a thundering backlash. "Balding, Wrinkled and Stoned" was the less-than-flattering strapline for a Time magazine last month, one which painted a picture of a generation whose continued proclivity for illicit drugs is embarrassing even their children.

In a barrage of new books, too, social critics from both right and left are taking aim at the new middle-aged. "Boomergeddon" is the not-too-subtle working title of a new book being written by the American sociologist Mike Males.

In it, Males will agree that American boomers have smuggled their free-thinking, hell-raising values into middle age, but argue that, as a result, they are the fastest growing demographic group to be involved in serious crime and the most likely to have HIV.

In his book Balsamic Dreams, published this week in the UK, the American satirist Joe Queenan accuses baby boomers of self-importance, narcissism and selling out.

The boomers, he argues, lived it up on state subsidies in their salad days and are now determined to kick away the ladder of social security for everyone else. Their determination to be different, he says, has turned sour and embarrassing.

He pokes fun, for example, at the way in which American boomers are customising their own funeral services into a mixture of stand-up comedy and karaoke.

Queenan and Males make interesting reading, but they do need to calm down and take a valium. The problem with the generational blame game is that it fails to do justice to the other things which motivate politics and social change.

In any case, British baby boomers do not have the same misplaced sense of generational solidarity as do their American cousins.

Quite the opposite. The irony of communicating with British baby boomers, as every advertiser already knows, is that many of them don't identify with themselves at all, but someone 20 years younger.

Maybe fresh-faced David Cameron is smarter than he looks.

James Harkin @ Guardian