(In reply to Lensman several posts above)
Well, it's kind of off-topic and I'm just a regular consumer with skimpy knowledge about this stuff. I can't explain everything, but I'll relate some experiences instead..
I do feel more secure with my money here than when I was in the States but it IS frustrating and time-consuming as hell sometimes.
Paying for stuff in real stores and restaurants is the same as anywhere else -- sliding your card, signing the receipt, keeping the duplicate they give you -- it's just the online payment process that's usually a few steps more complicated.
For one, if you want to do any form of online banking, you need to have the certificate I mentioned above. The kind that's issued for free only lets you make purchases under $300(I think) per order. You have to pay ~$2 to get a 1-year certificate that lets you purchase stuff freely. They're issued online by most banks and tie in with our citizen# (kind of like the SS#), and you need to register all your credit cards, bank accts, etc to yours (you can only have one at a time), then save it to your computer/flash drive/cell phone.
I think I've been asked for this thing and the password I set on it about 95% of the time I made online purchases from a Korean site. Every time I lose the certificate data or don't bother to bring it with me when I use someone else's computer to make a purchase, I have to deactivate the old one and get another issued. I had mine saved on my cell phone last year and had to get it reissued 3 times because some sites didn't support cell phone certificates. The story goes on and on...
One thing that was really strange was when I lost my wallet on a bus for a day, I reported my cards lost. Luckily, the bus company found it and I got them back the next day, but when I went to the two banks to get them reissued, they just reactivated both instead of reissuing. One of the banks was Citibank! Strange? :-S
Anyways, about dealing with foreign businesses: from the consumer's perspective, I don't need anything special to order internationally from eBay, etc. -- just the same things you guys need. I'm not sure how domestic companies sell to foreign customers, though. I just realized that for the first time. 99.9% of Korean websites require you to input your citizen#, or, if you're a foreigner living in Korea, your foreigner registration# (it's a racist name but that's how they call it....) to register for an account. If you live in another country and don't have either, you can't get an account at all. I guess that's one of the big limitations businesses have here.
One exception to security is Paypal. They don't have the added security measures on their site, but I've been able to send and receive money from the U.S. with it -- maybe because they're still completely based in the States. I heard they're frowned upon by the government because of it, though. Even the Korean eBay affiliate, Auction.co.kr, doesn't have Paypal as a payment option.
Whew!! There are several more implications that will REALLY bore you to death that I won't get into. Hope I settled your curiosity a little bit, though