On my first business-trip to Japan, it took a bit of getting used to - guys kipping in the meetings. Frustratingly, we ended up having meetings before the meetings to agree what was going to be said. We'd then have the meeting, but because the company president or some venerable elder gent would fall asleep, we'd then have to have another meeting afterwards to fill him in on the bit he missed! Working in some Tokyo offices, the office juniors would be there from 6am to 8pm - but proablay spent quite a lot of that time asleep!
That said, the benefits of power-napping are well known, but it's like the 9-5 culture that unless you can be seen working at your desk, you're not actually doing anything - I mean you could be doing anything, like posting on cycling forums!