Dating in the Workplace--Do or Don't?

A friend of mine at the clinic is dating our boss (she's an associate, he's the practice owner). He's just coming out of a divorce and I'm afraid that if things don't work out that things could go badly for her since it's a small practice and we live in a pretty rural area without a lot of other good, close veterinary practices to choose from. He also has a tendency to give people the cold shoulder when he gets upset about little things...which in my mind does not bode well.

She says she's in love and that it's "forever" but honestly--what are peoples' thoughts about dating in the workplace? I make it a rule to never get involved b/c mixing personal and private never seems like a good idea. Anyone with any personal experience...speak up...I need some advice on whether I'm being an overbearing friend by telling her it's a bad idea (or whether it REALLY IS a bad idea)!