I was playing on one my dps characters just doing a daily quest and this guy a Tank was quite serious in trade chat about his service as stated. This set off a firestorm of debate in trade about the comment, the situation and LFD queues and the ethics of creating a problem with doing so and fostering it in and of it self. It lead to some lively discussion in trade chat as a result. But with as many players playing WoW this can't be a original idea either and I'm sure some others are doing so. And I know I've been in 1 or two instances as dps where this happened as well unknowingly where the tank just all of a sudden just dropped out for what seemed no reason at all.
I really don't condone the practice as a Tank at heart myself and much against this as a practice for all the problems it can create. It can set some very bad future precedent in LFD, among others waiting in queue among groups itself. If you zone in and quit on any group you should suffer some consequence by Blizzard in the LFD queue as a result, no matter which role you play. That's just bad practice all around to other people in the LFD queues and don't help the current problem much either.
As for myself a person who has played a tank role for a long time and at heart someone who really enjoy the role to be quite frankly these days even though I can do heroics I just don't queue up for all my own reasons. I enjoyed the many months of stress free time away from WoW and i'm enjoying not returning all that quickly back to that role. That sure don't help you or anyone else much waiting for a Tank, group, heroics and long queues in LFD.
For sure the discussion on Tanks and LFD will rage on.