The only speculation I have read that made sense to me was this:
The group from "the boat" on last weeks show is asked to eliminate one of that group. The group that stayed at the hotel is asked to eliminate one of them. Obviously, Melanie would go from the hotel group, and Desire? would go from the boat group. This may explain the photos of Melanie and des standing last, Beau and Amy all pissed off looking, and why the show sent half the group on an excurition and left the other half home. We do know for sure that two members leave. This would be great because it would even things up.
Does anyone else get the feeling this show doesn't even know what the prize is yet? It's like there playing it by ear week to week. Maybe they didn't think the show would still be on, like it would have been cancelled by now. Why the HELL wouldn't they announce the prize?? I also think they know the majority of people like "the good guys" and they will manipulate the show each week to see that Keith, Dave or Charla wins. At least I hope so.