This could easily degrade into a rant because the urge to rant is what prompted me to make this post, so let me preface by saying I'm not leveling accusations at a class/spec in general.
Vigilance is an awesome tanking tool that was given to Protection warriors. It brings them on par with a paladin's Righteous Defense and in certain circumstances can be way better. An attentive warrior throwing Vigilance on a healer can avert a wipe. A savvy warrior putting Vigilance on a high dps party/raid member can not only boost the maximum dps potential of that player, but can benefit a bit in their own threat generation every time the dps damages a target.
In certain situations, putting Vigilance on another tank in a raid can be a brilliant strategy. Warrior tanking whelps/elementals in OS, slimes during the Grobbulus fight, or any other situation where a warrior might be required to pick up multiple mobs from a variety of places on the game field make Vigilance a neat ability to have access to. A pair of warrior tanks in a raid putting Vigilance on each other is an awesome way to ensure that no mob strays for more than a second or two at any time.
Here's the kicker, however: Vigilance on another tank is a debuff on that tank, so it stands to reason that it should be used selectively and in cooperation with that tank. Putting Vigilance on another tank in a raid without mentioning it to them is poor, poor etiquette. Putting Vigilance on another tank in a raid and then using it as part of an overall strategy to flex your e-peen and taunt a whole group of mobs onto you while the other tank stands there wondering wtf happened is weak. Very weak.
Apparently, there are a lot of warriors in raids these days that see it as their entitlement to put Vigilance on whomever they want whenever they want because hey, why not? The trouble is that Vigilance, while a benefit in some situations, is not more than a crutch in others. If you're a protection warrior and can't for the life of you figure out how you would manage without Vigilance on another tank at all times, I'd like to respectfully suggest you read a bit more about protection warriors, their roles in groups, and how to best go about filling those roles. Right now, Naxx is pretty cake-like in terms of potential tank threat vs. threat generated by your run of the mill dps class. We don't know what we're going to find in Ulduar, so it makes sense that nobody...regardless of class or spec...become too accustomed to abusing certain abilities as crutches.