Seems like millions of dogs eat them without harm, only an occasional dog is hurt by them, but i don't have any need to take the risk at all because Zack has plenty of other things he is happy to chew. Having Greenies would not add to the quality of his life.
When i first got him, greenies are one of the things i got at the pet store on the way home when i stocked up on stuff that first night, and i gave greenies to him, little puppy sized ones, he liked them ok, but seemed to like bully sticks more than anything. He also liked dental chews i got at the vet.
Then i started reading things about tragedies with greenies, heart rending stories of healthy dogs dying after first suffering terribly, grief stricken owners filing lawsuits, so i took them away, and put away the bag. some time later, Zack apparently found a greeny that had been stashed somewhere in the house that i didn't know about . I found out about it when i found him vomiting. There was something bright green in it, and a piece of a greenie on the ground. I have no idea why it made him vomit--maybe he swallowed a piece that was too big, i guess that would be the most likely explanation. Shortly after that, there was a loose stool with bright green color in it. This confirmed my determination to avoid greenies.
Zack is not a strong chewer, he never did chew up his first bully stick after he'd had it for a month or two. He doesn't destroy his toys, he still has some of his first cloth squeaky toys. But he can break small pieces off of a nylabone, the hard nonedible ones for strong chewers, so i dont' give him hard plastic chews.
He has other things he loves to chew so it's just not necessary to take a risk. If it depends on the dog as to whether greenies are a risk to them or not, then i would say that I got a red flag on zack when he vomited part of a greeny and also passed it in his stool.