I agree that going into a relationship with the express intention of making another person jealous is unfair, though I don't suppose that ever stops anyone. Love makes people a little bit crazy.

If you're not ready for a relationship, then like I said, yes, it CAN be unfair on the other person. But really, if you're going into a relationship with them, you should discuss your situation with them, at least to the extent that they know you've just broken up. If they know, it's just as much their choice to enter the relationship as yours.

Besides, not every relationship is long-term. If I'd just broken up, I'd like to date and have a few short-term things just to enjoy being free again. If no one's expecting commitment, no one will get hurt. It's my business who I date, when I date and what I want from that date.