Philadelphia has a few well-known incidents that are always brought up in discussions. (No snowballs at Santa yet?) However, I think somewhere along the line Philly fans got this reputation, and now every time something happens it just gets added to the List of Stuff We Always Cite Against Philly.
The truth is, every city has dick fans...or at least New York sure does. I wouldn't know about other cities since they don't travel en masse to games in Phila. However, I remember a Phillies game back in '92 -- at Philadelphia -- there was a Mets fan in the outfield stands who saw Dykstra about to make a catch and chucked a beer bottle at his head. I've generally experienced Mets fans to be horribly classless, so I'm glad the Phils sell out their stadium and don't have to deal with those dips as much any more.
I remember a Sunday two years ago where the Giants were visiting the Eagles during the World Series and the Yankees were visiting the Phillies. The Daily Show did "reporting" to determine which city had the worst fans. There was some measure of agreement that the two cities were at the head of the class, and yes, I think Philly did ultimately win out, but they also had homefield advantage. =p
I'm personally not upset over the Giants winning. I expected the Giants to win. I think this whole "Dream Team" crap needs to stop, and Vick was also not 100% going into the game. Add really bad tackling, and...yeah.