BBC's Mastermind tags itself as 'TV's Toughest Test'.
I think not. When contestants can set their topics as the 'Life and Music of Cliff Richards', and Grand Prixs from the 1980s till today, this is hardly a difficult competition. All it requires is a slightly frightening level of fanaticism. I'm sure any of my old pals in ATXF (aus.tv.xfiles community) could probably have entered (I'm looking at you, RachREL and Chris) and won every game.
Yes, there is a general knowledge section but those questions are no more difficult than those on Temptation, and frankly, I still think actually sitting through an entire episode of Big Brother would have to be TV's toughest test.
Mastermind sounds like ABC's Einstein Factor, http://www.abc.net.au/einsteinfactor/
As you pointed out, it does require a certain... dedication.. to your chosen subject - tho' EI contestents also need a fair level of general knowlege as well.
Oz BB is trying to drum up public interest in yet another season of incredibly boring people shrieking at each other; so far it doesn't appear to be grabbing the punters. Could this the end of fishbowl TV (please o'merciful deities!)?