Is it a coworker? If so, then you shouldn't worry. He's traveling, making professional contacts. Facebook can be a networking tool for many people. Chances are, it's a coworker and not someone he met at the hotel bar looking for a quickie the next time he's in town.

Honestly, I can't imagine any guy would be dumb enough to cheat with a woman who is also his Facebook friend. It's all to easy for his girlfriend or wife to contact that person on Facebook. For the love of Mark Zuckerberg, you could post a message on her wall. Unless he's a complete idiot, he's not going to cheat with anyone he knows on Facebook.

If it really bothers you, ask him about her. If he gets defensive all of a sudden, then maybe you should be suspicious. If you have an open and honest relationship, he should be fine with discussing his Facebook friends. As my esteemed colleague John Devore often says, Facebook isn't real life. Just because he's "friends" with someone, that doesn't mean they are actually friends (or more than friends) in the real world. We shouldn't always assume the worst. Jumping to rash conclusions will put a strain on the relationship.

Like you said, he travels for work. He's bound to make new friends and professional contacts, and adding them on Facebook could be a part of that. Talk to him, but realize that this is what you're getting into with a boyfriend who travels for work. You will worry yourself sick about every little thing because he's away from you for long periods of time. Is he in touch with you as often as he can? Is he a good boyfriend who does everything he can to make you feel comfortable with the fact that he has to travel for his job? If so, then don't sweat a new Facebook friend who is probably just Janet in marketing at the Utica branch of his company.