Let me quote Brickhaus from his excellent piece on this topic over at Bad Left Hook:

What is a robbery in boxing?  Here's a hint - it's not a decision that you merely disagree with.  It's a decision that is impossible; that there's no reasonable way the judges could have scored the fight in favor of the fighter who actually won.

Without having reviewed the fights, we can safely say Sanchez dominated round one and Guida takes round two based on positional control.  Round three is the most contentious with, in my opinion, Diego getting the better of the striking and Guida getting top control late (after escaping a Sanchez back mount attempt) but not doing much damage or any positional advances.

So, you have two things to decide.  Did Sanchez dominate the first period enough to warrant a 10-8 score?  And who does round three go to?

With that in mind, there's no way you can cry "ROBBERY!" about this decision.  The third round was close enough that you can't give it to Guida conclusively.  Even if you do, Sanchez can still steal a draw with a 10-8 first.

In addition, this fight doesn't expose any flaws in the ten point must system.  If anything, it exposes the flaws of 3 round main events between two guys who have the capability of going 10 more minutes.  With title (read: money) implication on the line, it's extremely unfair for fighters and fans to have fights like this be left to such a high variance format as the three round fight.  Add two rounds, reduce the importance of each individual round, and give us more opportunity to see a decisive finish.

The Ultimate Fighter 9 Finale coverage