Who is doing it, where and how. I am in the process of looking for places to keep panthers and the like outdoors all year. Are you using supplemental heat?
Can't keep them out all year but I have left hoehnelii and calyptratus outside when the temps have dipped into the very low 40"s. Hoehnelii even stayed out into the upper 30's. Once the sun came up and they had time to warm up no problems. Daytime temps rose into the 60's. If the weather was cloudy I would bring the cages in for the night.
You can keep chams outdoors almost all year in much of Florida. Your really only limited to panthers and veileds though, but there are some other members of Furicifer and Chamaeleo that would do well also. Below 45 degrees F in the winter is to cold for them and above 90 degrees in the shade in the summer is to hot so would have to stay between these temps. There is one member that I know of (Lizardlover, S.FL) who keeps some chams outside all year and many others such as my self, who keep chams outside 6-9 months out of the year.