The Dodgers/Giants rivalry ever since it came to California is pretty intense (I could imagine more so when both teams were situated in NY), but I think aside from a few incidents (i.e. a Giants fan being killed by a Dodger fan in '03, Steve Finley's walk-off pennant-winning grand slam in '04), the rivalry isn't that unfriendly, in my opinion. You'll still hear trash talk or harsh words exchanged between Dodger and Giants fans at the games that turns into a matter of why Norcal is better than Socal and vice versa, but that's all really. I remember when I was in college, campus seemed to be flooded with Giants fans and/or Norcal natives and it seemed like some or most of them were so snobbish, they didn't want to mix any verbal jabs at you. While there's a rivalry, I find that there's this prevailing Californian attitude of "I won't mess with you if you don't mess with me" which kind of waters down the intensity of it all. But that's just me, seeing how I look at soccer rivalries in Europe and South America as the yardstick as to what makes a rivalry filled with bad blood.
It's kinda like the Old Cafe - http://fbc2.freeforums.net