(Psst, try not to double/triple post, Zex.)
As for me, I've always been a bit skeptical of the Fight Centers, myself.
I do understand why they're created: They're groups of roleplayers who like to spar and have a chance to show off their roleplaying abilities in the case of a fight, and in some cases, there can be advantages to this.
Of course, it can be good roleplaying practice. There are usually those who watch over the group and make sure no one's godmodding. So, they're teaching good skills to have in any roleplay setting, to have respect for another person's character, even when your characters are fighting.
However, as it's been said, animal fighting is still a touchy subject.
Making these Fight Centers gives a bunch of animals (realistic or not) a very human side, and not the 'good' kind of humanity, either. It could even be said that it's an encouragement and desensitization toward violent behavior.
Instead of your characters having a reason to challenge one another, they simply go at it and try to inflict as much damage on their opponent with no reason. In a way, it's contrary to nature, and can take on a cruel, sadistic outfit.
That's the part that gets me.
This said, I've never been very fond of Fight Centers.
I can see why some people like to join them, but in many cases it gives a sense that these individuals and groups are blind to the graphic, cruel, and very real side of animal fighting.