Look around at the neighbor houses and see how tall above ground level their lights are. With exposed wiring, make sure you know what your snow removal pattern is going to be and what type of equipment is likely to be used. A snow blower can easily grab a wire and then all hell will break loose.

I don't know about people stealing them, it does not seem to be much of a crime here in Alaska anyways. I have seen people during spring repairing outside driveway and sidewalk lights though because of tear out fro shovels, snow blowers and truck plow guys.

Good luck on the project, at least if your able to get it going you will know what needs to be altered for next year.