Anonymous
As long as you didn't sign up, you are not responsible. My mom died with credit card debt, and the issuers came after dad. He yelled at them over the phone to get lost. If you don't KNOW 'em, you don't OWE 'em.
?
This one is tough, I mean you really don't want to break up with him over this but even if he worked extra hours and got the thing paid off on his own (which might be unlikely) then you still have to wonder when he'll do it again. I guess I would suggest a nice long talk with him about financial responsibility and about communications in a relationship. Figure out a plan where he will cover this debt he has incurred and tell him this is his only "pass",he pulls something like this again (and without even telling you) and its over - not because its that bad (though its bad) but because you can't have a relationship with these kinds of secrets floating around.
If he can get it paid off himself (even if you have to help a bit at the end) and he promises not to do anything like this again then I guess you can move forward. If he won't accept responsiblilty for this (or says he will but then doesn't really do what he needs to fix it) or does anything like this again then you may consider moving on.
The saying "Once a cheater, always a cheater." comes to mind, and though he's not cheating on you, this is sorta similiar (doing stuff behind your back) though not nearly so bad.
oklatom
Not sure why you are upset or what your questions is. It really des not affect you if he does not pay it, it is his debt not yours.
You can of course ask him why he did that without telling you he did if you want to.
Anonymous
Why did you marry a criminal?
You can call the police. What he did is a crime just as if some 3rd party you did not know did it.