Nano has been around a long time, and there were a few netbooks with them. At the cost of a bit of power consumption, they had a decent performance advantage over Atoms. I suspect that Intel had a hand in really making things ugly for Via in the market. IIRC HP had planned on ordering a few hundred thousand Nanos for their first HP Netbooks in 2008, but cancelled their order and went with the Atom at the last second. Intel was probably able to undercut whatever offer Via made to HP. It would've been a great win for Via in the market.
AFAIK Via does enjoy quite a bit of business in embedded and very small system markets. Where I work, we have many Via powered, Linux based "terminal-like" computers that interface with outside servers in order to provide us what we need. The actual computer is smaller than a typical hardback book in volume.
I would love to see Via truly break out though. I would be very interested in a quad-core Nano if it was ready for the market already. However AMD's future Krishna APU is the superior proposition.