The Repeat Poster
Most Likely To Appear: While scanning Twitter, gchatting with two friends, and blasting Waka Flocka Flame
Few people are less considerate than The Repeat Poster. Yes, some threads get really long and it's hard to keep track of everything that has been said, but the very least you can do is scan it over one time before jumping into the conversation. Hastily throwing in your two cents is Bush League at best. Not only does it contribute nothing to the thread, but it's also bad email etiquette. One violation is excusable, anything thereafter deserves some sort of public call out.