Richard Poynder has published "Open Access, Almost-OA, OA Policies, and Institutional Repositories" in Open and Shut?. This is part one of a planned two-part post.
Here's an excerpt:
First, I want to discuss how many of the documents indexed in "open" repositories are in fact freely available, rather than on "dark deposit" or otherwise inaccessible
Second, I want to look at the so-called eprint request Button, a tool developed to allow readers to obtain copies of items held on dark deposit in repositories.