One of my co-worker's cats had a litter of kittens. He kept them in his barn and accidentally left the enclosure he had them in open. Well... a racoon of all things got to them and only one survived. A RACOON!
Sammy was a semi-feral cat when I found him hanging out on my property for several weeks a year ago. At first I fed him outside and left him there. Slowly I let him come in at night and had him sleep indoors. The more attached to him I got, the more I worried about him being outdoors. Finally, I kept him in 24/7 to the point where now he doesn't even try to go out anymore. As long as he has his window perch where he can watch the squirrels and chickens during the day, he seem to be perfectly happy staying indoors.