I've gotten two perspectives on the subject from a couple of acquaintances. Example One could only be classified as a womanizer. He made no attempt to disguise the fact that he entered relationships for the sex, and was completely disinterested in long-term commitment. His problem was that he objectified it to the point where he nearly forgot that an actual human being came with the naughty bits, and ended up offending and hurting several girls by being completely insensitive and essentially using them. This came back to bite him in the ass when he encountered a girl he had real feelings for, and she rejected him because she knew about the way he usually handled relationships.
Example Two, a girl, was the victim of someone like Example One, and avoided commitment specifically because she was afraid of the other person using her. Since then, she's been going at it with whoever strikes her fancy, swinging both ways to boot. She doesn't do it for a momentary thrill, though; she remains friends with most of her bunkmates and seems to genuinely enjoy the intimacy. When an open relationship is that consensual, I suppose I see nothing wrong with it. It's just a different sort, and not something that should be condemned so quickly.
Personally, I think it's best to wait until you meet someone you truly care about, simply because it's a rather momentous occasion, and one that should be valued rather than taken for granted.