Anyone who's ever taken a First Aid course has recieved the following line of instruction "Never tell someone to dial 911, always single someone out. Telling someone specific to dial 911 has a much higher chance of success". You (point someone out), dial 911 and come back, seems to be the chosen phrase. This kind of follows the thought process of "Everybody thought somebody would do it, so nobody did".
This same reasoning can be applied in raids, especially when things have gone sideways - or you need someone to do a task that could be considered "un-fun".
Assign someone specific
This holds doubly true when assigning a task that requires a high level of personal responsibility (say, cleanse bot), or will drastically reduce their personal DPS (block breaker on Sindragosa). If you ask "who's breaking the blocks", you'll be met with a wave of silence that could crush Godzilla. Instead, assign the task to someone specific.
Raid leaders (or at the very least, your heal lead if there is one) should run some type of addon that will track major cooldowns like Rebirth, Lay on Hands, etc. A glance should tell you whose battle-rez is available, allowing you to call xxxCatDruidxxx to get someone up - instead of calling for just anyone to do it. Simply stating "get Jimmy up" will result in one of two actions, either multiple battle-rezs will be wasted - or Jimmy will lie there for another minute. This will generally cause your blood-pressure to shoot up 50 points, which isn't healthy for anyone.
Dig deep and volunteer
Know a tough job is coming up? Just saw a healer get folded? Volunteer to fill the role before someone has to assign it. Not only will you save someone a small headache, you'll show that you're paying attention to more than just your personal DPS/HPS. This all ties back to having Situational Awareness, and knowing what's going on all around you. Something as simple as typhooning a mob back, while momentarially inconvenient for a tank, may save someone's life. Ultimately, it's worth much more than losing a mob position for a moment. Note, I'm not advocating running around doing this all the time - I cursed GC when typhoon was first introduced.
My own moment of fun
Last night on our 25m Rotface kill, our kite tank DCd right as the pull happened. I tossed up RF, and called out that I was kiting the oozes, which I'd honestly never done. A quick judge/Holy Shock combo got it on me, and I was able to keep it out of the raid long enough for the tank to log back in. While this could have been handled by anyone really, by thinking quickly I helped prevent anyone from dying to loose oozes, and let the DPS focus on their jobs. By calling it over vent, I allowed the other healers to pick up my slack on the MT, and things went smooth from there.
I also picked up my 30th Val'anyr fragment (much thanks to the raid leader for organizing this, and the guild for participating), and since nobody else wanted them - I have the pieces for making a Shadow's Edge now. It'll be useful when I'm Holy/Ret and leveling in Cata - or at least for some PvP shenanigans.