Undine asks about this article (registration req.) from the CoHE, which speculates that "[s]enior scholars, the A-list of academic publishing, seem to submit fewer unsolicited manuscripts to traditional humanities journals than they used to." This possibility isn't new at all, I'd say. When I worked for Modern Philology in '97-'98, the journal's senior editors were already chewing over this topic: many of their friends chose to go with edited collections, not journals. The reasons I heard then and have heard since are many: it's easier to target a collection than a journal; there's less hassle involved; invitated submissions are always nice; etc. Moreover, while it isn't true that edited collections aren't peer reviewed, the peer review tends to come after the article has been accepted by the collection's editor--meaning that there's much less time-to-acceptance (or rejection) involved at the front end. I should add that MP was not besieged with articles while I was there, despite the journal's age and relative prestige; the non-existent backfile caused some alarm (would we actually run out of articles?), although it certainly sped up the rate at which articles appeared once they were accepted.