On Ebay I look at the buyer's feedback. I look at the things they buy and who they are transacting with. If I feel comfortable about that then I go ahead and make the deal. Having said that I won't usually try to sell or buy anything of high value on Ebay. About the highest priced item I have sold there was a $1500 cue and that one went to the USA.
As for PayPal - I do use paypal all the time and knock on wood there has almost never been a problem. Once last year on a $1500 sale paypal froze the money until the buyer completed some steps, but I knew the buyer personally and so it wasn't a problem.
There are a lot of paypal horror stories and generally they tend to freeze first and ask questions later. When I had my merchant account and someone would initiate a chargeback the card processer would send me the info and give me x-number of days to provide my proof. They wouldn't take any funds back until I had a chance to prove that the sale was legitimate.
I don't like to keep too much in PayPal for this reason. I have just signed up with PayMate which is a credit card processor without the monthly fees. They deposit directly to your bank and as far as I can tell provide more protection to the seller in the case of chargebacks.
I will say that I have sold dozens of cases to people all over the world and had no problems whatsoever with any of the payments through paypal.
The only times I have had to chase the money is when I sent something out without getting paid first.
I guess the best advice is that you have to try to get to know the person you are selling to by doing as much background as you can before you pull the trigger on sending out the product.
By and large I would say that Europeans and Taiwanese are ok to deal with. I sell to Singapore, Thailand, Indonesia (although there are a lot of scammers from there so be careful), Taiwan, Japan, Germany, Spain, Poland, France, and Holland and to date have had no issues.
Well, once case was stolen in transit but that's it. It was insured and I just made another one.
So, insurance is a must!