a) That legal/acceptable?
It seems to be as far as Sony is concerned. They turn a blind eye to it at least.
Create a new user, and then register them on the PSN under a different region. I have 3 users, one for Europe, one for US and one for Japan. Registering as a US user is easy peasy since it is all in english, though you may have to provide a dummy address (Beverly Hills, 90210 is quite popular I hear
). You'll also need a different email address to register each user.
Japanese registration is a little trickier due to the language barrier, but there is a guide here:
http://blogs.ign.com/xheavenxsentx/2006/12/09/39684/
c) How does that kinda thing handle credit cards?
I have a european mastercard, and last I tried a few months back, I could use it on the US store, but not on the Japanese store. Other types of card don't seem to work. IIRC, there was a way to get european cards working on the Hong Kong store, but I think they may have closed off that opportunity. In the absence of a working credit card, you'd just have to wait for PSN prepaid cards to become available, or make friends with some users who're willing to share content with you (there's a mechanism that allows you to share most of the games on the PSN store with up to 5 other people - something Sony provides and supports, it's not a hack or anything).
Other thing to note is that with multiple accounts, you can access any downloaded content from any account, which is nice. Indeed, you can even log in to one account, start a download, and then log into a different one and your download will continue, and you'll be able to start another download from a different store if you wish. Just don't delete your other accounts, though, as doing that will disable access to any content you downloaded with them for all other accounts.
