Theoretical physicist Terry Rudolph shares a story about preprints and the editorial process at a top science journal: "Guest Post: Terry Rudolph on Nature versus Nurture". In short, there was no problem posting a potentially interesting physics paper on the arXiv, and then getting it reviewed by the journal. But when the authors posted a follow-up preprint, it sabotaged the "interest" of their first submission:
While it mildly rankles that my own participation in that “wide debate” was curbed by the blurry lines of their own policies, I’m not particularly upset by the episode – perhaps indicative of my well documented own laissez-faire attitude to publishing, but perhaps because I know the result is ultimately more important than the journal it appears in.
The ironic part is that Nature wrung the news value out of the first preprint with coverage from its news division. Rudolph's story gives the appearance that the journal was happy to promote the work before it accepted the paper, but later claimed it was not newsworthy.
I don't really have any problem with journals pursuing papers that are newsworthy. My problem is that these journals make papers appear newsworthy by their control of information flow. I've said it before ("The costs of publication delays"): We need to eliminate the myth that publication itself is a newsworthy event.