Saw a blurb on Dr. Oz about the nasties in cow-harvesting-assemby-line burger meat. The guest expert was ringing a large alarm bell regarding pink-to-red burgers. Burgers that are not "overcooked" are the rage right now.
Now, I am sure that many chowhounders know the names of the cows that they eat. (Exaggeration) Seriously, I sometimes go to a butcher that takes more care about the beef they sell and their burger is yum and I don't cook burgers from them all the way through.
But do you really trust all restaurants to be that careful with their sourcing? Or do you say "medium-rare, please" and hope for the best?