I do freerange mine when I'm home. I live in a heavily wooded mountainous area with all the predators you can imagine, including roaming dogs. We even had a fox's den on the corner of my property about 200 ft from our coop and the kits were coming out of the den by the time we knew it for sure.
I know my time is coming to lose one, but in two years we've owned chickens, no losses. Part of the credit goes to my rooster, Hawkeye, who is the best warning system and bodyguard my girls could have. Part of it is that we are most often home and in and out of the house with the girls quite a bit. I have CDs strung on mason's line over the open pens, which reflect and make it hard for a hawk to make an easy dive by the physical barrier of the crisscrossed string and the blinding effect of the flashing CDs. Other than that, it's been sheer luck, I guess.
Edited to add: They are locked up tight in pretty much predator proof coops at dusk every night. A bear could get in, but a bear pretty much goes wherever he wants to go anyway. A human predator could get in but we'd probably hear him over the baby monitor trying to unbolt the stiff barrel bolts that go vertically and horizontally.