In all honesty, I really think that 'normal' people make the best housemates
Ok, they're not always the most exciting... But the more normal the housemate, the more private they are - The longer it takes to really know them. It becomes more of a progressive story with standard housemates. Of course, it's a TV show; we do need the big personalities but it works to juxtapose these with a few underdogs that need almost unravelling.