I think you have to have common sense about whether to range your birds or not and where/when. Prior to my getting chickens, I watched my neighbor man do everything wrong and his birds disappeared one at a time till he only had 4 of his original 18 left within a 14 month period. We have seen foxes in our front yard, have a pair of barred owls living in our oaks, have tons of hawks, had racoons, skunks, and opossums on our back porch, and even seen coyotes. Now, those same trees that house the owls also seem to deter the hawks: We have about 2 acres of sweeping live oaks with low twisting canopies. I have seen hawks make several attempts to dive into them without success...so we put the coop, run and pasture under the trees. We also put larger animals that do not like anything/anybody they don't know in with the chickens in their pasture.
I have a 100x300 fenced pasture that the chickens share with four decent sized goats and sometimes a cow or horse: If my nanny goat doesn't know you...you aren't getting in and that goes for animals too (she attacks our 90 lbs dogs and they are terrified of her). I have a dutch door (split in middle...top and bottom open separately) on each coop section and in the morning, after the sun is fully up and the owls that live in our trees have went to bed, I open the top door. The chickens that want to go out usually do so then and must fly and perch on the top of the bottom half of the door. They stay out till late afternoon, early evening when they all return to their respective coops to roost. I usually have to put the last couple guineas in at night and then close the doors and secure the latches. During the day, half the chickens stay in the pasture, but at least 1/3 of them venture all over the property: Our cat keeps a pretty good eye on them (doesn't bother them at all...never has). Also, our guineas are pretty good at defending against death from above and have saved our ducks before: It was awesome to watch them beat that hawk down.
When I started letting the chickens out, I had a couple times somebody stayed out till it got dark: They couldn't seem to find their way home (probably since they are night blind). So, we installed a 25 watt light bulb in the coop. Since then nobody has stayed out past curfew. In a year and a half I've only lost two chickens: One bantam Dorking rooster that didn't get back into the coop before dusk and the Barred Owls got him (he was rehomed here and didn't follow routine); and one Golden Campine that went over the back fence and never returned (added to the top of that fence).
So, if you can let them out in an area that is safe: They will love you for it. If you can't then as others have said...just bring them treats from the outside and they'll still love you for it. Just use your common sense: Nobody knows your property and predators like you do. Even if they only get out once in a while, anything beats life stuffed in a cage on a production farm.