Dogs should be eating what their wolf ancestors ate. Raw meat and raw bones. People that feed raw know that their dogs are healthier than ANY dog fed kibble, it shows in their eyes, coat and teeth. They have higher energy and live longer.
If that were the case, I'd hate to see how much energy Tango would have on a raw diet. I know dogs who are fed raw (ex: Tango's mom) and dogs who are fed kibble (ex: my dogs). Tango & her mom have roughly the same energy level (Tango's a little more active), both of their coats are beautiful, both of them have great teeth etc. Without asking the owner of both dogs what they're being fed, you'd have no clue whether they were eating a raw diet or kibble. I'm not saying that raw is a horrible diet, in fact, when I move out I'd like to possibly switch my dogs to raw but I also see nothing wrong with feeding a quality kibble.

Anyway, back to topic....

I don't give my dogs greenies simply because they're extremely expensive IMO and Tango & Winston don't like them. However, I don't think they're a horrible poduct. Like others have said, you just have to supervise the dog if you're going to give them something such as Greenies, rope toys, rawhide etc.