According to BGR, Apple's internal support system confirms that the new 11-inch and 13-inch MacBook Airs are experiencing display bugs in some cases. Both the flickering and fading are known issues, although there's no real fix for them—yet.
Apple employees have been told to say that they're aware of the problem, and that a software fix is "upcoming." In the meantime, you're encouraged to put the computer to sleep, wait ten seconds, then restart the computer to force a display power cycle.
It's still not clear whether the new MBAs were shipped with a higher bug incidence than normal, but enough people have raised the issue that the company has formulated a formal response. It could well just be a very vocal minority; if my screen were doing this all the time, I'd shout about it, too:
Let's hope a software fix is all it really needs. [Boy Genius Report]