I disagree. I think guest lecturer still are a position of authority, but there are degrees. HP CEO was fired for dating a contractor or something like that. Where is the line?

Also Bill Gates.

Anyway, my personal wish is coworkers should never, ever date. There are so many options, why take one that has the potential to blow up? Yet, it's one of the common ways people meet. I even knew one who married a woman he interviewed and hired. If only we could all be more logical about relationships. :/