This happens all the time, but this one really made me laugh. Using my full Dread Guard Assasin tank with the Warstalker title. Right at the start of the FP a DPS in Columi and the healer both pop out "grd plz". Good thing people try and keep the flashpoints entertaining.
I had the exact opposite today. I was healing a random hm on my fully optimized DG-geared Scoundrel. The tank was in level40+ leveling gear and so was the shadow DPS he insisted on guarding. I kept ripping aggro off him purely with my heals, so I asked for a guard. He refused each time, stating that only the melee DPS should be guarded. Funny how it can go the other way around.