If users make choices on a website or product you can log these choices. And from those choices you can try to extrapolate what tv programs, dvds or books that particular user might also like. Amazon suggests other books you might like and TiVo (the addictive digital video recorder) suggests other programs you might like, based on your viewing behaviour. And of course we're all dreaming of the home of the future, that has already fills your bath before you even realised you wanted to take a bath. Now wouldn't that be nice?

But as always the devil's in the details. What if the profiling algorithm goes astray. Here's a story to illustrate: If TiVO thinks you are gay (Wall Street Journal, subscription required, but here's a rip). A quote:

Mike Binder, creator and star of that show, had set his home TiVo to record his 1999 movie, ”The Sex Monster,“ about a man whose wife becomes bisexual. After that, Mr. Binder's TiVo assumed he would enjoy a steady stream of gay programming. Unnerved, he counteracted the onslaught by recording the Playboy Channel and MTV's spring break bikini coverage. It worked, he says. ”My TiVo doesn't look at me funny anymore.

His wife, however, was taken aback when she saw all the half-naked women he was ordering through TiVo. He told her those women meant nothing to him: ”I'm just counterprogramming because TiVo thinks I'm gay.“