Thanks to Denise at the New Pages blog for bringing up the question of anthology merit. Although I couldn't find the responses, she did post a follow-up which included a comment that covered at least one of the major issues with the glut of narrowly-focused subject matter anthologies:
From Dinty W. Moore, editor of Brevity :“I honestly don't know the answer, but thanks for asking all of the right questions. If an anthology ‘packager’ doesn't at least have a plan to find distribution, it seems unlikely anyone will read the book other than the authors and the authors' friends. Which begs the question: if a book falls into the forest of books, and no one hears it fall ...”
Of even more significance to me is the screening process (anyone who submits is printed versus a merit based filtering), which is inescapably linked to more issues - will the anthology weather time? are the contributions representative of the highest creative voices or simply representative? is the anthology intended for its contributors or a wider base of readers (the distribution question fits here)? is the anthology simply a revenue generating effort for the editor/publisher (something Denise brings up) or more cynically, a route to false kudos in the land of special interest publishing?
I'm leaning toward a weaning of the anthology glut. Accomplishing this in the era of electric messages is the first challenge.