I think it was pretty clear it was Annie from the start. Even at the vote, 10-0 shows the house guests knew. Ragan even admitted he knew it was her in the elimination vote. Now what people at home were thinking was another story. They thought Kathy was the saboteur with 21% of the vote that is split between 13 people? What show were they watching?
The question I'm wondering is if the saboteur was lying saying that two house guests are actually already friends. I think it's the truth since it would bring another twist for CBS and be a back up plan if the saboteur (Annie) sucked, which she did. So I will take a chance and say that Ragan and Matt are the friends and they are really more than just friends.