I don't know what could be more obvious than a black cross in front of a yellow square.
I three agree with this.
Maybe you haven't played Medic yet, but its pretty damn obvious when theres a downed teamate nearby.
Don't just think for yourself. As the post before me said, they could be out of supplies, they could be trying to heal a higher priority teammate, they could be close to fulfilling an objective and worst of all, the area in which you were incapacitated could be too dangerous for the medic to attempt to revive you. Medics shouldnt have to face certain death on occassions to heal another teammate because its more detrimental to the team. If the area is full of the opposing team and you peer pressure a medic into healing you and he dies, surely one of the opposing team will spot that you were thrown a revive syringe or even in the process of reviving and they will kill you with ease. 2 dead teamates sure isn't better than 1. Theres nothing worse than a teammate selfish enough to rage everytime they dont get revived.
But then again, Im biased as I play Medic, but thats just how I see it.
/endrant