Increasingly wondering what publishers do for science and research

It seems that researchers are increasingly using Open Acesss (OA) platforms like Arxiv or Nature Precedings to disseminate their work. Authors often submit their pre-print manuscript version to these sites or to in-house depositories, for example Enlighten at the University of Glasgow. Researchers are at least encouraged to do this by funding bodies and research institutions.
This often means that the article is in circulation before the publisher's nicely formatted version (see for example, Rod's Elsevier Grand Challenge Paper) and begs the question "What do the publishers do for research and the scientific process?".
Ten years ago, it was easy to see the role that publishers had, they disseminated your work by convincing libraries and individuals to subscribe to their journals. In this way, your research had a chance to be seen on a few library shelves across the world after a few months of format checking and page layout with the publisher. But now, the worldwide web does that for you and does it immediately!
O.K., publishers do play an important role in the review process. They make sure they get a famous and qualified editorial board who select good papers for review and choose good reviewers for the job. This increases the impact of the journal and so feeds back into the status of the journal and the publishers. But increasingly, this seems to be the only thing that publishers are providing and could be done by other institutions like universities.
It seems that publishers have caught onto the fact that things are changing fast and they need to do something about it. One solution is to enrich the readers experience of a paper if he reads it on the publishers website as opposed to the pre-print pdf version in these OA archives. This, I think, was the idea behind the Elsevier Grand Challenge and perhaps behind the PLoS Hub for Biodiversity . There is no doubt that we are in need of better ways of finding research and data with the ever increasing number of publications to keep up with.