I just found this real quick:
Processed Cheese
Processed cheeses are made by cooking the whey to extremely high temperatures, killing all bacteria and microflora in the product. Unfortunately, this technique also eliminates all of the flavor, requiring the cheesemaker to add flavor back after cooking. The advantage to using this technique is that processed cheese does not require refrigeration and has an extremely long shelf life. The disadvantage is that processed cheese has no character, no healthy properties and an unpleasant gummy texture. Examples are Kraft Singles and Laughing Cow.
http://www.igourmet.com/cheese.asp