I believe the harm in leaving raw meat uncovered in the fridge is that more bacteria will enter, more oxygen will enter (causing faster bacteria multiplication), and more water will escape (causing dryness which probably slows bacteria multiplication, but toughens the meat, so let's consider dryness to be bad; I'm not making beef jerky). Please ignore the stinky odors that escape; just consider the quality of that one uncovered piece of meat after we eventually cook it.
How much faster will the food spoil (percentage, compared to the same meat wrapped in plastic wrap)? I imagine that meat with skin, like a whole chicken, is not effected as much as meat without skin, like a bare chicken breast, and that ground meat would be effected the most. I wish I had some data to convince my roommate to cover his meat; is there any research on this? Feel free to answer this for milk instead if there is more research for it.