Does Jealously Make for Good Friendships?

A recent study out of Arizona State says jealousy is what keeps some friendships afloat.
The study suggests that envy motivates us to be a better friend. Specifically that they might like their other friends more than us. This typically happens in the form of a third party threat, when another enters the picture. But, interestingly enough, most are more concerned over a new friend versus a love interest. It comes down to the threat of being replaced.