A very quick post tonight, but I've had an article published in The Conversation titled Open-access science: be careful what you wish for.
To cut a long story short, I fully support this move. I would love my science to be read by all (well, at least those who are interested :).
The caution is, however, that doing this costs. The current funding model is a bit busted; scientists need to publish in established journals, as articles that do not appear in the "highest impact journals" are not considered as important.
But the journals are owned by big publishing houses, and so libraries need to pay for access to the papers, often to see the science generated by their own researchers. It's a bit of a complex mess.
Anyway, my caution is that while the funding for open source science has to come from somewhere, it is not good to raid existing science budgets, when those funds could be used to support more science and innovation.
Raid existing budgets? Surely you think this is not possible, but check out what's recently happened in the UK. While I support the move to open source, I'd rather see money being spent on science being done, and we think of clever ways of making it accessible to all!