This has little to nothing to do with stopping scammers. It is all to do with trying to stop traders who provide games to and from different regions.
I have traded for games before and saved money. I couldn't have gotten those games otherwise, and with the changes valve have made in the last few months I wouldn't have been able to get them for the price I did.
They are determined now to stop this trading, no matter who it affects.
I understand they want to stop people from getting games for less than the retail price in their region, but since most of the time the person will either buy the game cheap or pirate it, then they are better off allowing the cheap sales to those few people.
It won't gain them a full price sale. The games I have saved money on I would never have bought full price. I would have probably torrented them to try them out, and then if I thought they were good enough I would have waited for a sale.
And these things affect people in general sometimes. Granted no often, but sometimes. And if you are an honest consumer, you should never be negatively affected by things your service provider is doing to stop people saving money.