However, I think its only supported on Mozilla Firefox.

I used to support it on my media sites when Mozilla was topdog, but since the share is split between Chrome/IE I no longer do so.

Does it hurt to support it? As in, why did you stop supporting it if the infrastructure was already there?

Oh its not that. When I re-wrote the pages, or upgraded services, I just stopped including/thinking about prefetching for Firefox.

So it pretty rapidly disappeared from all the sites that I support/operate.