I just answered a question from someone asking if it was "safe" to rent a property on homeaway, since it had been advertised since 2010 and had no reviews. Did some additional research and found an interesting article in Forbes. It explains that an owner can have HA take down all of their reviews as an alternative to posting a negative review. This would explain a lot! I don't know how to add another answer to that same question, but hope that Lisa R. Sees this!
http://www.forbes.com/sites/maureenfarrell/2011/01/20/homeaway-and-vacation-rental-by-owners-confusing-review-policy/