Remember those free routers by Fonero? These routers, 10,000 of which were sent out for free recently, are overheating and some actually melting. This video is of a particularly monotone man and his melting Fon experience.
It is also noted that he isn't the only one dealing with some hot fon problems. A lot of users on the Fon message boards are reporting heating issues, none of which seem to be as extreme as this guys', but nevertheless, a melting router is never a good thing. There is no official work from Fonero, but I would probably suggest disconnecting if the router is getting melty or unusually warm.