It's GROSS
but won't hurt your furbaby. Usually they do this for one or a combination of the following reasons:
1. They're missing something in their diet, and eat poo to try and get whatever the missing mineral/vitamin/nutrient is. What kind of food are you feeding?
2. Their food goes through them undigested, so the poo still smells like food to them, so they eat it. (Again, what are you feeding?)
3. They are trying to cover up the fact that they pooped, because they don't want to be scolded for it.
If you can figure out the cause, you may be able to remedy it by changing your action or changing their food. A higher quality food might do the trick.
Also, you can purchase ForBid from your vet, or Deter from PetSmart-both are vitamins you either sprinkle on their food or give in pill form that will make their poo taste "Bad" to them, and they won't want to eat it anymore. I have also heard that you can sprinkle Meat Tenderizer or MSG on their food to help with this, though I haven't tried it. I have two poop eaters
and the Deter from PetSmart (1/2 tab per day each) will stop the problem temporarily. Usually with poop eaters, you can stop it for awhile, but they will do it again eventually, and you'll have to break the cycle again later on.
Just remember that though it's way gross to us, it's not harmful to them.