I’m sure someone’s made this observation before, but lets look at scaling math for WOW group content.
5-man: 1 tank, 1 healer, 3 dps. 20%/20%/60%.
10-man: 2 tanks, 3 healers, 5 dps. 20%/30%/50%.
25-man: 3 (often less) tanks, (7) healers, 15 dps. 12%/28%/60%.
What’s my point? Simple. The number of tanks needed does not scale up fluidly from 10-man to 25-mancontent, yet WOTLK has made many more tanks available/viable. This has led to anoversupply of tanks (though skilled tanks are always in demand.)
Dual Spec! I urge all tanks–invest in a dps altspec, gear/enchant/gem it appropriately, and learn to dps well. You don’t necessarily need to be able to do top dps, but it makes the raid leader’s job much easier if he can mix and match tanks based on the fight, rather than “well guess the warrior’s tanking everything since he has no dps spec and he does crap dps.” The raid will flex around you, to a degree, if you’re skilled, but you’re cheating your guild members if you allow it to happen too frequently.
Edit: Or druids/pallies, altspec heals and offer to let a healer switch to dps. They will LOVE you.