Why hasn't open access grown more? It may be because scientists in mid-career don't need for their work to be part of a culture war between free access and free submission, they want to be recognized so they can continue to do work they love - and that requires funding which requires showing the work is useful. It may be that print publications are pretty good at doing what they are supposed to do, namely getting important studies seen and so, like Blu-ray not really replacing DVD, 'good enough' is just that in publishing as well. Authors who don't want subscription journals to keep copyright can buy it out for slightly more than online-only journals, and still have the legitimacy of print but even then they rarely do it, 10% according to Jocelyn Kaiser in Science, August 20, 2010 (sorry, a subscription journal).
Another issue may be that open access on the back end is only part of the equation - cost has simply shifted from subscribers to researchers but research is not really 'open' if scientists have to choose between losing copyright entirely and buying it from a publisher, like the more popular open access journals require in the way of pay-to-publish fees. Logically, a number of scientists have to wonder why a movement has built up around the idea that reading someone's work for free, especially if financed using taxpayer money, but no similar movement has built up around publishing for free.
Basically, open access may not be taking off because it is just a waypoint toward 'open' completely. Whatever the reason, scientists don't seem to care about being more open, at least the way it exists now. It has been a matter of law for two years that NIH-funded research was to be published as open access but uptake is only 70%, and that is just a subset of government-funded research. Scientists apparently don't see a benefit.
Science 2.0 arguing against open access after endorsing it so many times? Not at all, I am arguing for open publication as well as open access. Print journals contend that a research article costs them $10,000 and that is their rationale for charging for subscriptions and carrying advertisements the way content magazines like Esquire do, but content magazines like Scientific American buy articles from writers and subscription journals do not. BioMed Central, which pioneered the open access model, can publish those same articles for $740-$2,380 online and be profitable but why does it even cost that? The answer is people; programmers to build a repository and editors to look things over and then maybe some server cost.
But scientists are fine with government being in the science business and funding the overwhelming majority of science in the US and the government is also already in the publishing business without a problem. PubMed Central is run by the U.S. National Institutes of Health and is completely free and, as I mentioned, NIH research already has to be in it. So why not use it and eliminate all fees, both in subscription and submission, for life sciences research? That would make science truly open and it would be terrific proof-of-concept.
Peer review is done for free in both subscription-based and pay-to-publish journals so there is no additional cost there. People who like to do peer review will continue to do it and the PubMed model could later simply be expanded outside life sciences.
Open Access has been a good first step but Open Publishing, where publishing is free and access is free, may be the way to go to truly change the way research is understood and shared.