Yeah, I can't do it. We have fox around, and plenty of community cats (one evening, I walked down the ravine looking for our dog after he ran off, and I shined my flashlight upward to see about 6 pairs of eyes staring at me). We had a cat get some sort of blood borne disease, we think she got it from a tick that was in the house when we moved in (it's our only theory, we have no idea what actually happened), and she spent a few days in the animal hospital, and barely survived. (It also cost several thousand dollars.) Unfortunately she passed away from multiple medical issues a few years later. :(
(We adopted another cat after she passed - we've never had more than 3 at once.)