How do they determine it? Not very well, obviously- there are a lot of deceptive ads out there that have been running for a long time. When you hear something like "If it snows, it's FREE!", but then find out when you walk into the store that it has to snow more in 3 hours than it ever has within 500 miles of that store, you know it is deceptive and that you've been had. But you're there already, and the law of percentages says you still might buy. There should be hefty fines for this kind of marketing.

No, in fact they put themselves in peril when they do this. Even though most states have requirements &/or disclosures that must be given to a buyer before signing any contract, this situation puts the buyer in a position of being "represented" by an agent who already has a relationship with the seller.

Even though many experienced agents are very capable of handling this situation with complete professionalism, less experienced agents could have the possibility of favoring one party over the other if a complication arises during the transaction.

This will have NO impact on your costs or the price of the house if it is already listed with a broker, because the seller has already signed a contract estabishing what commission they are paying (regardless of whether the buyer has an agent or not).

If you're a buyer, it is always best to be represented by your own agent/broker and have someone looking out for YOUR best interests.