the game will be about focus. ray lewis is the heart of the ravens. you don't think the team won't be ready? crabtree's legal troubles might be a problem. also, 49ers are younger. the media frenzy might be a bit much for many of them.
Don't forget that the Baltimore Ravens have never lost in a Super Bowl appearance. ;)
I will be shocked, though, if the 49ers do somehow lose the game. (Plus, it would mean that the Ravens would become the only team in NFL history to appear in more than one Super Bowl without ever losing instead of the 49ers current streak.)