Yes, apparently it is really common and I've seen it in our dogs too.

Dogs are scavengers/opportunists by nature so if they come across a stool that is palatable, they might decide to eat it.
Meaty diets create more attractive stools than dry diets.

In one of my dog behaviour books, it says:

"Yet, for the dog, coprophagia is not usually a problem. It is simply a case of a scavanger maximizing his intake and taking advantage of a nurtient source."

It also says:

"Of course there may be increased risk of gastric upset or parasite infection for dogs which engage in this behaviour but otherwise the main danger is that the owner may reject their dog as a result of it."

In the UK, there was a series of pet health helplines set up one time and the most rung line by far was the coprophagia line.