My cats can go outside if and only if it is broad daylight, and someone is in the house (or preferably outside with them). We also keep careful track of who is outside and who is inside. We would NEVER leave the house, go to sleep, get in the shower, etc with them outside! We are very careful about that. We also live in a suburban neighborhood with very kind neighbors. I've never seen a leash-less dog around here. And we have a large area behind our house with no other houses where the kitties usually go. Our cats are also young and healthy and can get up a tree if need be. All four of them were either found as either strays or feral cats, so they are used to being outside.
We also had a cat for 16 years who had free indoor/outdoor roaming, and nothing ever happened to him. He died of kidney failure - not caused by any dangers from outdoors.
I agree with keeping cats indoors all the time, but our cats love the outdoors so much that we have to let them out occasionally - especially because of the constant screaming we get from them if they are indoors and want out.
I actually would prefer to leave them in all the time, but my mom insists on letting them out. I never do it myself.