At my job, I always feel like it's frowned upon to take a nap. In most cases we're a "as long as you get your work done, we can be flexible with hours" kind of shop. But the moment I close my eyes even for just a few short moments, someone either taps me or later mentions "man, you look exhausted, are you okay?"

Power naps make me feel more refreshed, which I'd assume people would want out of their coworker/employee late in the work day, but maybe I'm wrong.