Yeah, would be awsome! In XBOX LIVE for example you can "dislike" people which decreases their representation (shown as 1-5 stars), this also decreases the chance of getting connected with them again as enemy or teammate!
Re-connect function for people who have unstable internet would be also nice
My feeling with this is it gets abused so you have people disliking someone just for being better than them, but I suppose it's an improvement on anything we have now.