Careful. Sony's figures for PSN user count are worldwide, and a large percentage of Sony's market is in Japan alone. The CSN appears to be USA and Canada only.
FWIW, Japanese much less commonly have or use credit cards. It's one of the reasons eBay failed while Yahoo Auctions succeeded in Japan, by not requiring a credit card to list.
Yep. If you're travelling to Japan, don't plan on using your credit card to pay for accomodation - in my experience, you'll need wads of cash.