As a seller, I have refunded gift payments and requested they get resent as regular paypal (at the same amount they paid previously).
As a buyer, I wouldn't pay via gift if fees were 13% and the seller wanted them to be 'my' responsibility. The 3% I have paid as a buyer in private sales paid for itself (and most of the fees I've had to pay since) the first time I had to make a claim (someone tried to sell me a fake Photoshop license. I had the money back the next day).
I really don't see the 'incentive' for a buyer to pay via gift. You're basically saying 'sure, I don't care that you can basically keep my money and not send me my item.' while simultaneously saying 'haha, I didn't have to pay Paypal for their services', if your transaction goes as expected.
The real thing that sucks is that if / when Paypal decides to do anything about this (such as severely restricting how often and to whom you can send money via gift), it will likely involve a raise in fees as well, and the people that were previously using gift will simply switch to another service to try to manipulate to save that 3%, while basically ruining it for the people that play by the rules (okay, in absolute fairness, the people that scam other people are the ones that would ultimately be causing a scenario like this to happen, but at the same time, people that are willing to attempt to skirt the rules to save a few buck would at least partially be to blame as well).