Not the same has putting a deterrent on a sign on your property. I'm guessing electric fences aren't just for farms, but folks put them around their gardens to keep the deer out, etc.
“Oh my! I electrified the sign because the deer kept nibbling on it - I never imagined a person coming onto my yard and messing with my sign!!”
That would be ok if was marked but if the sign itself was electrified and wires hidden so if you grabbed or otherwise ground the sign you got shocked then that would be a trap. Thats why electrified fences are all equipped with warning signs.