When you enter the academic world, you realize of one surprising thing: it’s a rather opaque world. In fact, many of the most prestigious journals make their publications only available to subscripters, so the only part that is available on the web for free are their abstracts.
So in the era of Internet and free access to information, scientific knowledge obtained through research (which should be the paradigm of free access to knowledge) depends mostly on an previous outlay.
At least until now. The Research Without Walls movement allows the research community to pledge to assist in the peer review process only for conferences and journals that make their accepted publications available to the public for free via the web.
Right now, the number of subscribers is not very large, but the list of institutions they belong to is pretty impressive: Google, Microsoft, Berkeley University, etc. And their prestige is important, since the reputation of conferences and journals is mostly determined by the researches that assist in them. The fact that they refuse to collaborate with closed-access publications may be a great boost to the free access to academic contents on the web.