The rivalry reached new heights in 2012.
The Niners edged the Seahawks by a half-game to win the NFC West last year. However, Seattle's Week 16 destruction of San Francisco, 42-13, has left in doubt division supremacy for 2013.
Where there is no doubt is the dislike between these two teams and their fans.
The following are some reasons 49er fans have to hate the Seahawks. It's meant to be all in good fun. I'm sure there are many more I'm missing.
At USC, Carroll was notorious for running up the score on opponents. That, by itself, isn't a big deal to me. But when you're known for doing it, you shouldn't be mad when someone tries to do it to you.
In 2009, Jim Harbaugh and the Stanford Cardinal scored a touchdown in the fourth quarter to take a 48-21 lead. Harbaugh went for two to try to get to an even 50.
After the game, Carroll was visibly upset with Harbaugh for running up the score:
A few weeks later, Carroll and the Trojans did this:
See the double standard?
Also, Carroll left USC in ruins to become head coach of the Seahawks. Although he's not the first college coach to leave his program in tatters, he still shouldn't get a pass for abandoning the Trojans the moment they were hit with adversity.
Lastly, watching Carroll genuinely celebrate one of the worst calls in NFL history and then tell the world in the postgame presser that it was the right call drove all NFL fans crazy (even if I don't blame him for being excited for winning the game, illegitimately or otherwise).
Tate, in an interview with 710 ESPN in Seattle, said he wants to give Harbaugh, "the Sean Lee treatment" (h/t Pro Football Talk).
So, in other words, he wants to blast Harbaugh when he's not looking.
Real tough, Golden.
PED Users (Richard Sherman and Brandon Browner)
What's especially not cool is Sherman didn't get suspended because of a technicality.
Also, Browner apparently wants to "put his hands around Harbaugh's neck." What ever happened to a normal fistfight to settle things?
Overall, six Seattle players have tested positive for performance-enhancing drugs since 2011, according to Mike Florio of Pro Football Talk. And this caught the attention of Jim Harbaugh, as well as many 49er fans.
Avril has a reputation for being a dirty player. The 49ers seem to get the worst of it.
Vernon Davis told Matt Barrows of The Sacramento Bee that Avril, when playing for the Detroit Lions in 2012, gouged his eye after a play. And Anthony Davis said Avril attempted to rip off his helmet in the same game, which isn't surprising considering the postgame Twitter feud they had a year earlier.
He's way too good a quarterback for a short, third-round pick. That is all.
The 12th Man
Before I go any further, I must say that the Seahawks, and the Pacific Northwest in general, have great fans. However, it gets so loud that many have wondered whether the Seahawks pump crowd noise into CenturyLink Field.
You be the judge.
And the 'Hawks took the "12th Man" phrase from Texas A&M (among others). A new, more original moniker is long overdue.
The head coaches don't like each other. Both teams are serious Super Bowl contenders. And they're division rivals.
Essentially, this rivalry is destined to be heated for a long time.
I'm sure Seattle fans have plenty of reasons to hate the 49ers (Harbaugh No. 1?). But it's hard to argue with the collection of hate-inducing reasons the Seahawks offer to San Francisco fans.
What did I miss? Let me know in the comments below.