Bookies, not me, have: Tipsy, Verdasco, Harrison, Mallisse, Dimitrov
Bookies never lose, so they say
Not 'never lose' but they're certainly right more often than not.
Tennis is a hell of a lot more unpredictable than other sports though, due to the individual nature of the sport and various match-ups. You never know when someone's going to play the match of his life, or who's going to just not turn up. Then you have to factor in different surfaces and conditions. And then sometimes it's just hard to tell how good someone actually is (players hampered by injuries like Brian Baker or Hewitt, or younger players like Goffin and Janowicz who made massive ground last year). Some younger players are far better than their ranking, but just haven't realised their potential yet and will often 'spring an upset'.
Part of the reason why I love the sport so much.