Gossip

Whether you call it blackballing, shafting, waysiding, snubbing, trash-talking, or rejecting - in the end, it boils down to gossip. The practice of ostracizing someone through social intercourse and in such, convincing others to do the same is done so through gossip. When you talk about someone behind their back and tell others about how someone has done something wrong to you, to others, what have you, that is you spreading negativity regarding that person amongst others. You are spreading gossip. You may not even have all the information or facts on the matter at hand. 

This behavior is viewed as very immature when done in an OOC capacity. Whether you are sharing this information in AIM, email, on the Forums, in a PM, in a Hobbitmail, on Helpfile, in the OOC communication channel, or on another game even, it is inappropriate. 

If the gossip is IC and it is born between characters, not based on something OOC said, done, not said, or not done, then it can exist ICly where it belongs. Do NOT take OOC, whether from another Player or Staff, ICly and make something of it, likewise don't take an IC situation OOC. Keep them separated.