groupthank
The act of "replying to all" on an email chain just to specifically thank one individual. While usually well intentioned (and intentional), the practice often becomes an annoyance to everyone involved.
Person 1: "Did you see that Nicole just groupthanked Brian on an email chain with 120 people?"
Person 2: "Well, at least it's better than what she mistakenly replied to the entire staff after the 2007 Christmas party!"
Person 2: "Well, at least it's better than what she mistakenly replied to the entire staff after the 2007 Christmas party!"