Do Magazine Covers Still Matter?

Rob Walker wonders:

Once upon a time, of course, it was a declaration: An authoritative statement from the experts about What (or Whom) To Talk About. But how often do you actually see the cover of Time these days, anyway? And what does the magazine’s cover choice communicate to you on any given week? 

He thinks it indicates an authority that we haven't quite figured out how to replace:

Arriving at some kind of replacement for that would involve a consensus not just about what has authority this second, but about what has authority that could plausibly endure.