Good idea in theory, bad idea in practice. Implementing it to the game with no restrictions will have people adding people for minor disagreements. Adding it only for certain players will cause an uproar about people being biased or unfair that only a few select people may use them. Giving it to official factions only will make independents and unofficial factions whine about it too.
All in all, great idea. But I can't see it happening. Remember we live in the world of the internet, and some people here act without thought of consequence or respect for their fellow human beings. In an environment such as this the tool will be abused, and we don't need more rules to control its' use.