I interned at Google's Mountain View HQ in 2009 - I don't remember there being an actual nap room, they just had a few nap pods (like this http://www.hammacher.com/Product/12199) scattered around the office.
plus there is something about lying completely flat that is especially conducive to sleep, at least for me. I slept better in an overnight bus in China packed with bunk beds, than in most airplanes.