We don't leave any toys out unattended. The jolly ball seems to be a toy that is appreciated, but I have observed that our goobs have the most fun when I pitch it out for them and "play fetch." They seem engaged when there is human interaction.
I always remove the jolly ball after each 'play' session, because I've noticed that our baby likes to stick her foot/leg through the handle. I have no idea whether she could snap a leg, but I don't want to risk it. ...especially, since the vet couple that lives nearby put a horse down after it broke its leg. I had this idea that horses' legs can be fixed up with a cast or whatever, just like humans, but apparently that is not always the case. To me leaving toys littered around is not worth the potential risk.
By the way, I had read about the plastic milk jugs used as play toys. They seem too flimsy and I didn't even try it, because at one point one of our de-icers failed so I was hauling out water in 1 gal. plastic jugs. Out of curiosity, I let Baby nibble at it and it took a only a few seconds for her to figure out how to rip a chunk out of the bottom while I was holding milk carton. I pried her mouth open and removed the plastic chunks, but based on that experience, I just really can't see that a plastic milk jug is something one would leave out there unattended.