[James]

I think in the early series the contestants were still fame-hungry but the difference was that many of them thought they would get media-jobs out of it. The housemates now know they won't get presenting work out of Big Brother but still want the red-carpet, famous-for-being-famous z-list status.

If the producers want a wider range of personalities there has to be more incentive for people to apply for the show in the first place e.g. financially. At the moment, for example, there's no reason why anyone with any kind of career would go on Big Brother - especially with the series running for longer.