116
Google Fiber is offering early access to $250 per month 20-gig service - The Verge
(www.theverge.com)
This is a most excellent place for technology news and articles.
Meh, you can do 20g over a pair of bonded sfp+. My cheap-ish Zyxel managed switch will let me do this
Even assuming you could do this, and your backplane even supported it, most of your end devices are still limited to 1 GB NICs, so you would need a large amount of people utilizing your network for this to make sense.