Found a picture which indicates a really stupied route for this movie.
http://www.chud.com/index.php?type=news&id=7050
Based on this picture, Sandman is the original killer of Unlce Ben, which will cause Parker to seek revenge. This desire is enhanced by the black costume. I personaly think they could have done better than saying that Sandman was the one who killed Uncle Ben.
First off if Sandman was even there at the scene, why wasn't he in the car with the robber from the first movie? I just think its a horrible ploit twist. I think that if they were going to have a reason for Spidy to want revenge have Sandman kill MJ, Dunst doesn't want to do Spidy any more anyways so kill her. Let MJ and Gwen Stacey trade places since she is the route of a love triangle in this movie. For the most part MJ has replaced Gwen in terms of major events in the Spider-Man mythos.