On the whole, college football coaches get along because they understand each other better than anyone else.
But there are a few relationships that were fractured on the recruiting trail or because of past dealings.
In the case of Mack Brown and Bob Stoops, it seems these two have faced off so many times that there was no choice but to have some bad blood develop.
Not all of the great coaching rivalries are bitter or even long-term; some are the byproduct of where they coach.
Here's a look at 15 of the best going today.
Until Michigan and Brady Hoke actually beat Michigan State, Mark Dantonio can hold on to bragging rights.
But these two know the importance of winning this annual matchup, and you can guarantee that they don't have the most positive things to say about each other on the recruiting trail.
Since Hoke and Michigan earned a BCS bowl win this season, you can beat Dantonio will use the lack of respect for his program as a motivational tool.
Now that Lane Kiffin has a win at Autzen Stadium on his resume and USC is now eligible to win the Pac-12, you can bet these two are ready to duke it out.
Chip Kelly is still the more respected of the two, but they are competing for the same players, and both rosters are stocked with talent.
Can Kiffin make it two in a row against Kelly in 2012?
I can't wait for the showdown at the Coliseum.
Todd Graham coached on Rich Rodriguez's staff at West Virginia for two seasons, so they have some history.
But now they are taking over at rival programs, and you can bet they both understand the importance of winning this annual game.
They will also recruit against each other for some of the best players in Arizona and the region.
The edge has to go to Rodriguez.
It's hard to decide whether this is really a rivalry any more; Steve Spurrier is clearly superior to Dabo Swinney right now.
Spurrier gets the best recruits in South Carolina and seems to win all of the time.
Swinney did lead Clemson to the ACC championship, but the Tigers aren't up to the challenge of the Gamecocks.
Neither is Swinney.
Dana Holgorsen and Mike Gundy are friendly rivals.
Holgorsen was an eccentric offensive coordinator at Oklahoma State and went on to become a first-year wonder at West Virginia.
Now that the Mountaineers are headed to the Big 12, it's going to be interesting to see how these two former colleagues will fare on opposite sidelines.
I'm not sure if these two have ever been close.
But after Mack Brown politicked hard for Texas to play in the Big 12 championship game in 2008 while Bob Stoops sat by quietly, you have to believe the level of respect was diminished a bit.
Yes, Oklahoma lost 45-35 to Texas and still played in the conference title game and BCS national championship.
These two have to recruit hard against each other also, so some of the things said on the recruiting trail have to get back to them.
The moment Ohio State hired Urban Meyer the Buckeyes showed how powerful their football program is.
It also signaled to Michigan coach Brady Hoke that he is going to have to work extra hard to keep verbal commits this season.
Hoke also realizes this will elevate The Game even more.
Right now, Hoke is riding high, but it could be short-lived with Meyer in Columbus.
When you coach at Alabama and Auburn, you have no choice but to publicly despise the other team and coach.
Does that mean Gene Chizik and Nick Saban can't share a Slurpee? Of course not, but I'm sure Chizik's would be orange and Saban's would be crimson.
You have to believe they respect each other, though, since these two men have the last three BCS national championship trophies on their respective campuses.
There's a good chance you could pick any coach in the SEC vs. Bobby Petrino.
I'm going with Missouri's Gary Pinkel since the Tigers found a way to steal top wide receiver prospect Dorial Green-Beckham away from Arkansas.
As a newcomer to the SEC fray, Pinkel and the Tigers need someone to be a new rival. Why not Arkansas and Petrino?
Since Lane Kiffin and Jim L. Mora were complete flops in the NFL, they should have a little sensitivity for each other.
But right now Kiffin is riding high, and USC is a legitimate BCS title contender.
Mora is taking over the rival UCLA team that is left in complete disarray following the failed run by Rick Neuheisel.
Mora has his work cut out for him, and in getting the best recruits to consider the Bruins he'll likely have to smear Kiffin's name a little.
Is it actually possible to create a more disparaging image of Kiffin? We'll find out over the next few years.
This one goes back to Nick Saban's days at LSU.
The Tiger fans have never forgiven him for leaving, and Les Miles has no choice but to follow the company line against Saban.
Plus, there are a lot of coaches who are just envious of Saban's success.
Now, Miles has nothing to be embarrassed about, but Saban casts a pretty big shadow.
Mike Leach is accustomed to being the second-class program at Texas Tech, and he'll face the same task at Washington State.
But Leach led the Red Raiders to regular status as a Top 25 program and a consistent bowl participant.
If he is going to do the same at Washington State, Leach will make life a little more difficult on Washington's Steve Sarkisian.
Sarkisian is still the top dog in the state, but he can't overlook Leach.
Mark Richt and Steve Spurrier have become the class of the SEC East.
South Carolina has won the last two meetings, and the Gamecocks could easily make that three straight in 2012.
These two teams always seem to play close contests, so the tension is high every time these two face off.
Frank Beamer and Mike London are both pretty classy coaches—but you know London would love to do anything to end Virginia Tech's reign in the state.
Virginia was much better in London's second season, but he must match Beamer and the Hokies with talent.
The Cavaliers may be getting closer, but it may take another year or two until they are real rivals again.
So, for now, it's all about Beamer vs. London.
This is a developing rivalry.
Will Muschamp was always following Gene Chizik after he left a job. He did it at Auburn and again at Texas.
The two defensive-minded coaches probably have something to prove to each other when they square off.
Maybe we can finally get to the bottom of who was the best Auburn defensive coordinator between these two.