We've used homeaway.com in the past and after the last time we had a disagreement with the rental owners (long story) after failing to resolve the issue with the owners I contacted homeaway to fill a complaint against the owners. They told me I had to send in a written formal complaint. I did that and a year later still haven't heard anything from them. My "review" on the rental website is the only place where you see that I had a problem with the owners.
I wasn't expecting homeaway to get my money back or anything, but I would have liked them to put a note on the renter's page. Just my 2 cents, but we obviously won't be using that website again.