Even if every single person on the planet has an ePlug mining at (generously) 1000 hashes per second, you'd only get 7bil*1000=7Thash/sec. Juxtaposing this to the current 300000Thash/sec the whole planet cumulatively would earn a few dozen usd per day.
Now ya see why I say farming will become preferable to mining. I love bitcoin, but mining it is getting tougher and tougher. I'll just hold it as a store of value. Over 21,000 companies accept bitcoin now too so its propagation is coming along nicely. Distributed computing is the future, imo so the ePlug mining abilities is just a cross sell, probably at that point more important for businesses anyway. Home users could probably care less about mining. Farming income will surpass that of btc mining income so in turn, that will encourage more people to get an ePlug just for it's distributed computing abilities. Sneakily, this is expanding the meshnet at the same time.. I'd love it if nobody every had to pay an ISP for their restricted access ever again.