> I cant think of any other site that uses it. Not Steam, not Google...
But you aren't selling stuff to others on those sites.
Amazon isn't having you do this for normal Amazon buying, right? Just for selling. So, it isn't the same as Steam or Google at all. Those are just worried about protecting YOU. Amazon has to worry about protecting OTHERS from you when you're a seller.
That being said, you could argue that EBay doesn't do it -- but that doesn't work as well because EBay lately is overrun with scammers. I've just had an order cancelled in the past week where it was a scam seller -- and my co-worker had one two weeks ago and still doesn't have his money back yet. So, EBay really DOES need better security -- like what Amazon is starting to do for their sellers.