Prefetching considered harmful

I've been trying to get prefetching working in an app I'm building at the moment, but Firefox has been consistently ignoring my wishes and only fetching on click. I looked in my about:config and, lo and behold, prefetching behaviour had been disabled. I didn't remember doing that? I turned it back on but it still didn't work. I checked about:config again, and it was disabled again . What?? To keep…