Not professional? So, what, if you're a work-a-holic I suppose you're just meant to wither and die since it's just not professional to go out with another work-a-holic at your place of employment. While you're at it, why don't you cancel all office christmas parties, and perhaps fire people if they try to engage in anything that doesn't involve work. Work is like, one of the best places to meet people with similer interests. Saying you shouldn't have work place relationships is cornering people into finding people they don't work with, and given the increasing working hours of most people, many people don't have the time to find someone else.
Besides, I met my girlfriend at work. Our managers set us up to go out with each other. Then again, this was at a fast food resturant, so I wouldn't look at them for high standards in professionalism. Still, the fact that you work closely with other people at work so often means that it's just easier and safer to find someone at work than some crazy/weird/sexual pervert at some bar.
In my opinon, work place relationships are the best out there.