Robert Poppenga: It is unlikely that melamine itself is causing the pet illnesses. The current thinking is that melamine in combination with cyanuric acid (another contaminant in the wheat gluten and rice protein concentrate used in the pet foods) may be responsible, although this has not been proven. There is no reason to add melamine to pet food - melamine is believed to have been added to the wheat gluten and rice protein concentrate to artificially increase their content of nitrogen (and as a result their apparent protein concentration). The more protein in the material, the higher the selling price.
David Brown: I think everyone is pretty confident in saying that melamine and the other compounds were not put in pet food for a purpose that was not, at base, fraudulent, deceptive, or possibly accidental. There was no high-minded "purpose."