They've done two in a calendar year before (2 & 3)...
Basically what LPM said. Part of the appeal is that most people WANT to be able to travel to many different places, and you look at this and think to yourself "Self, not only could I do this, but I'd actually have a blast doing so". You'll also notice that while there are alliances, they're generally quite temporary, and typically have very little impact on who goes home.
Probably no Sawyer-type on the show though. Sorry.
And man, Bolo's blown up faster than Billy Gunn...