What was it Ursula K. Le Guin called the majority of bestsellers in her recent Harper's essay?

Ah, yes.  Baloney-mill novels.

It looks like her essay is available online at the moment, actually -- but I'm not sure it's supposed to be there, if you know what I mean*.  If it's not still there when you look, you can find it in the February 2008 issue of Harper's.

*Maybe it is, I dunno.  But I didn't see any 'reprinted with the permission of' note.