Fires, indeed.
First time Dad and Uncle put up an electric fence, was with one like that. Being cheap, they didn't want to buy posts & insulators. Had a bunch of old galvanized water pipe lying around that they cut into 4 ft lengths and drove for posts, then cut strips out of of old tractor tire inner tube and wrapped around the tops of those pipes, then fastened the electric fence wire to the innertube with a piece of wire.
Didn't take long for those inner tube strips to start smoking! Evidently, inner tube rubber is not an effective insulator for an electric fence.
Deer running through the fence and knocking it down started more than one grass fire for us until the low-impedence chargers came on the scene.