Why ? Paypal can yank the money back if the receiver of the part says he never received it. So USPS would be out for me...I doubt the guy in SA would pay the $$$ to have it shipped UPS or even Fed-X. Direct wire transfer to your account is probably the most secure...they can send you money but there is no way they can get it out. I use a totaly seperate bank account for Paypal and keep the funds just low enough to keep it open. Paypal will not help the receiver of funds if there is a problem...I know for a fact..
That can happen with an american buyer too. I have more than 1000 ebay transactions, most of them purchases. I believe that feedback is still an asset.
Many times the seller will say: "sorry I only send insured", and many times, the overcost of insurance is close to the item alone! So I retort: "listen, it is stupid to pay 100% of the article price for the insurance, when the chances of it being lost are less than 1%. I run the risk, send it regular mail. Never had any problem, and if I had, I would have kept my word and declare the item lost.
Insurance protects the seller, at the expense of the buyer. If I'm the buyer, I want to decide if I want to run the risk. The ebay messages can act as a disclaimer for the seller, in case I file a complaint to Paypal. But as I did, I believe that when a seller sells me an item and I have plenty of positive feedback, it helps to win some confidence.
I understand it gives some uneasyness to send things to strange addresses, that some strange post company will deliver, so you will lose track of it once it flies beyond the US border. But there are many countries apart from US with honest people, honest postmen, and efficient post services. Overcome your fears and don't refuse to sell abroad, try first with low cost items. You will see that it can be a smooth transaction, the same than with a countrymen. And I personally enjoy the fact to receive things from other countries, so I guess many other people is dying to buy from US.
Not blocking foreign bidders means having more bidders, and that means more chances to have a bidding war and higher selling prices. The more restrictive you are, the less potential buyers, and so the lower price. You may get scammed every now and then, but if you check the buyer profile, at the end of the day you are better off selling worldwide.
Can you imagine if the chinese would sell only to chinese people? I have bought from chinese many times, the prices are ridiculously low, and the rate of loss is 0%.