I didn't have time to check if the following details have already been posted here but for what it's worth I found another hole in my browser that was feeding websites my geo location to help them personalize me.
In your Firefox browser address bar type in: about:config
Then search for: geo.enabled
Double click it to change from default of broadcasting your IP to disabling it -- if you want to make it a wee bit more difficult for those profiling you for commercial purposes.
I know there are many other ways for sites to get it just the same but after testing it on a google search page they are no longer displaying my local location in the left hand column.
I've read the info on this from that link you posted and it appears it's a rather useless feature from the perspective that websites that are willing to play nice and request permission are probably not the ones to be concerned about. Whereas those that are intent on tracking your movements throughout the day (mobile users) are not going to let a browser setting stop them? Or is this a feature that marketers having been whining about that MSFT is going to block by default in IE 10?