In the middle of an extended Q&A post the Fish from This Fish Needs a Bicycle has an interesting insight:

[Q] Are you a jealous person? – Kristine
[A] No. I’m an insecure person. It’s different.

It’s an important distinction. I realize that while I feel pangs of jealousy from time to time — the couple who made (and kept) just a whopping pile from the whole dot-com thing, the guy who plays great guitar while sight reading piano music — I’m not really that jealous. Insecure, though? Yes! I’m going to have to think about it more.

In the overt case it certainly seems like objections to infidelity have a lot more to do with insecurity than jealousy. (Or perhaps more accurately, people who confident in their relationships seem less concerned about their partners’ infidelities.) In less obvious cases I’ve noticed that people who don’t to want their partners to have any friends are at least as likely to be driven by insecurity as by jealousy or possessiveness.

Hmmmm.