What's Middlebrow?

Why would Louis Menand in The New Yorker (9/5/11) dredge up a term, "middlebrow," which made limited sense fifty years ago and makes none now?

Faux-radical Dwight MacDonald invented the categorization in the 1950's as a way to attack novelist James Gould Cozzens. MacDonald never explained with precision what the term meant.

Was Cozzens's Guard of Honor middlebrow? The novel is complex, knowledgeable, intelligent, subtle, challenging, and difficult. Ultimately, it has more to say about the creation of American empire than any novel written. High-brow? Not really. The work is grounded in real situations and people. It presents intelligence rather than intellectualism. But in no way could it be called middlebrow.

Is Jonathan Franzen's Freedom middlebrow? The Art of Fielding by Chad Harbach?

We're in vague territory. Categorizations according to "brow"-- perception and pose-- are more about standings within the society of letters than about works of literature themselves.