Why Open Access?

Open access is one of the hot topics discussed these days. I have recently commented about the issue in the context of ACM's position [link].  Editor Prof Vardi was kind enough to give me an opportunity to express my views. Apart from the views I express there, I also would like to point out the parallels with the open source software. Open access publishing currently viewed as just an access to article's content. Probably PLoS is the only model that goes beyond this, that one can leave comments on it after peer-review. I think this signifies future tendencies on peer-review, why a paper should be a static document? For example, largest preprint service arXiv supports versions on the articles. I wouldn't surprise if we adapt similar practices of open source movement under the open science umbrella; living peer-review and access to every details of the research. Well, it opens a big debate as well but looks like industry is embracing the value of openness, slowly.