The thing I like about Zerply is finding people to work with. Which is kinda the point of a professional network when you think about it.
It's only fairly new, but I think the value will come from endorsements more than connections.
If you're looking to hire a developer, does it really matter if you know me or know someone that I know. What's the point of linking to people you already know anyway?? If you're looking to hire someone, it's far more important to understand their reputation than it is to understand how you're connected to them.