there's nothing 'bad' about the yolk really. it is where all the fat in an egg is stored, as well as the cholesterol. it also has about 2.5-3g of protein.
people who have cholesterol problems, especially a genetic predisposition to high cholesterol (the bad kind) tend to shy away from egg yolks.
All I do, is use all the whites and some of the yolks when I make my daily scrambled eggs. usually its 1/3 of the eggs being used that get their yolks tossed in. So, 6 egg whites, and 2 yolks. It gives you a more normal tasting omlette or scrambled eggs...as egg whites lack flavor and body since they are just straight protein.
sometimes I cook up the other yolks and give em to my dogs. so i don't feel like i'm wasting 15 cents worth of egg yolks