Liane Jones: Getting ideas above your station? BB will sort you out

It's over. After a series that felt as long as an elephant's pregnancy, Big Brother Seven has finally ended. Runaway favourite Pete has won, the telephone watchdog is investigating alleged unfair practices and the psychology profession is making noises about whether its members should really be involved in this kind of thing. A triumph all round, then.

And if you hoped our appetite for reality TV might be dwindling, think again. Nearly eight million of us watched Friday's raucous final ceremony as, one by one, the last six heard their fate pronounced and walked out on to the scaffold to face ordeal by public acclaim or humiliation.

It was riveting, as it's been all along. Because being booed has a visceral power. We've seen normally tough contestants cringing and weeping as they've heard their name catcalled from outside. "Be strong," their housemates exhort, as they ease them out through the doors. "You're a good person; we all love you!" they add, conveniently forgetting that they nominated them for eviction in the first place.

Yes, it's all about judging and being judged. Contestants judge each other, the viewers judge contestants, and on eviction nights, the crowd - the noisy, placard-wielding representatives of Us at Home - delivers the reward or punishment.

Well, we have to get our fun somehow. In other eras, we screwed gossips' tongues into bridles, put nuisances in the stocks, and whipped troublemakers naked through the streets. Now we watch Big Brother or The X-Factor or How Do You Solve a Problem Like Maria? to see people put in their place.

So are we indulging in spite and gratuitous cruelty? Enjoying the spectacle of the pack savaging a weak member? Some people do recoil from the whole thing, never even watch Strictly Come Dancing, and spend their leisure hours avoiding the violent parts of wildlife documentaries. But most of us have been involved in at least one bout of trial by TV this year, even when we eschew lowest common denominator TV such as Big Brother for the more intellectually respectable Dragon's Den or The Apprentice.

My mother would never watch Big Brother, for instance, but she's hooked by How Do You Solve a Problem Like Maria?, especially the bit at the end where the finalist who's been voted off has to sing "Goodbye" to her successful rivals. It's classic Ordeal TV, a symbolic, humiliating punishment for failure.

But it's show business. And that's the point. The contestants want fame. They bring us their singing, dancing, business acumen, or their personalities, and invite us to judge. And we do. Not necessarily kindly, but then that was not in the contract.

As Simon Cowell said on his Desert Island Discs outing (roaring with laughter): "We're not drowning kittens. We're just telling terrible singers they're terrible." And after extensive viewing, on mature reflection I think he's right. Oh, I admit I've done my share of cushion-clutching as contestants have been lacerated by Cowell or skewered by "Sralan" Sugar or as they've had to walk into a cauldron of baying hate outside the Big Brother House.

And I certainly worried for Shahbaz when he left the House in tears all those months ago. But on Friday, there was Shahbaz at the final, braving the jeers so he could give his enemy Richard a vigorous thumbs-down. He'd chosen to come back to this 21st century version of the village green to pass his own judgement. "Never mind the counselling," he seemed to be saying. "Bring me a ducking stool." Now there's an idea for a series.