That wasn't the question he was asking... hes asking if you can have two completely separate .Mac accounts, not just email accounts, on the same computer. I would say... why? For $99/year you can get 1GB of storage added to a single .Mac account, instead of only getting 250MB + an extra email. You could mount 2 iDisks at the same time, but AFAIK, you could only setup OS X to "integrate".Mac accounts into all the shortcuts, etc, one at a time, but you could manually setup more in Mail, Finder, etc.