There is a possibility that there's been some match-fixing in some of the matches. I for one, didn't expect Brazil to get past the group stages. In any case since this would be bad for FIFAs image, I'm sure we won't hear much about this. There could be accusations flying left and right but that's about how far they'll go.
FIFA is relying on rulings the Cameroon FA will make. If the Cameroonians were paid to throw the game then the officials were in on it. The investigation to me, is a ploy to hoodwink anyone who may have some interest in the match-fixing claims so that any denial [of it happening] would be based on the findings the Cameroonian FA forwards to FIFA. Keeps FIFA in the clear.