Can I be held responsible for someones utility bill?
Potentially, yes. The utility company might look to you as the person in whose name the account is held. It wont be able to collect from anyone else. The person who used the utilities can pay, even though the utility company somehow refused payment. The two of you can go to the utility office together to facilitate payment. Or, if you pay, you may have a right of indemnity from the person who actually used the utilities.