You've gotten a lot of responses here. I've gone out and rented via finding people on message boards. This can be risky, of course, but there are a couple ways to vet the owner. Primarily, go to the Orange County property records, where there will be a record of the owner's transaction and prove that is an owner. And, of course, ask for references. Now, someone could fake his way through all of this, but taking those two steps will go a long way toward protecting yourself.
We've had excellent experiences. It's a great way to save money and I recommend it to anyone I know who is going to Disney and isn't a complete newbie.