I agree that if it's being fed just as a treat, it shouldn't cause any real probs. But I'd cut down the treats to one cob per horse to be safer, and I wouldn't feed it to any horse that was susceptible to laminitis.
Cereal grain, while commonly fed, is generally not great for horses. Corn is about the worse of the lot. It is indigestible in the horse's stomach & so goes thru to the hind gut to wreak havoc with it's very high starch/sugar content. This often leads to 'fizziness' due to tummy ache, colic, and 'hind gut acidosis' which is thought to be the leading cause of laminitis.