"Yahtzee" Croshaw's recent review of Cataclysm (hilarious, but very NSFW) pointed out two things about WoW that were of interest to me. The first was that, as a mage, I would die a lot less often in PvE if I remembered to use Mirror Image when I get into a tight spot. But second and of more general interest, he pointed out how pervasive the phenomenon of mutual congratulation for achievements has become in WoW, to the point where one could easily be forgiven for thinking that typing some variation of "grats" was a Pavlovian response to any achievement announcement.
I happen to think it is more of a case of social pressure, personally. You want to be congratulated when you achieve something worthwhile, so you do likewise to your fellow guildies. But then the question becomes: just how far do you take it? Do you "grats" at every opportunity, or do you pick and choose which ones are worthy of your typewritten esteem? Does seeing other "grats"-es make you want to join in, or are you perhaps the other way, "grats"-ing just to show that somebody appreciates the achievement just announced, even if it is just Shave and a Haircut?
How you decide when the time is right to type those five little letters into guild chat?