Well, you can live on credit cards in Japan so long as you don't mingle with normal people (i.e. eat at nice restaurants, shop at nice stores). You *can* recharge a Suica with a credit card but it can sometimes be difficult to find a ticket machine that takes credit cards. Most JR stations have such machines, I think, but the subway is basically cash-only.

The other thing that might trip you up is taxis. I have always had trouble getting foreign cards to work with taxis. (Then again, I have trouble getting cards to work with taxis in the US as well...)