I really don't think the results were tampered with; as others have noted it is as much a popularity contest as anything. Even discounting the audience voting, going into the last night Stacy was down by 4 points in the judges scoring so despite a perfect score she still would have lost to Drew. The overall outcome would have not changed; she would have simply been eliminated later. It's too bad, because the judges really did say that she had the most talent of any. She got screwed on her freestyle, which was weaker than Drew's. Still, she was scored lower because of 'expectations', not because there were specifics to be judged against..
To make it less of a popularity contest, the audience vote should not be FOR a dancer, but AGAINST. Think on that a moment. Right now you can have a Jerry or Master P 'fan club' pack the voting for their favorite, no matter how poor. If the voting were against a star, the block vote gets fractured; there's no way you could expect a fan base to all eliminate the same person, but those who felt that Master P should have gone out in week 2 (as I did) would certainly have voted that way. A decent dancer with no fan base like Giselle Fernandez doesn't get penalized for that; it's more a case of not liking somebody's dancing.
I should note that I thought that Stacy was by far the most elegant and graceful of the dancers; Drew knew how to work a crowd..