We open access advocates are unanimous in the goal of universal open access to the world's scholarly knowledge (at least in its peer-reviewed journal article form, for now). However, at times we differ about the means. Some of us favor a focus on rapid transition to a fully open access, more efficient and effective scholarly communication system - what some call the gold road of open access publishing, and Harnad refers to as the premature gold rush. Others, like Harnad himself, favor beginning with the traditional scholarly publishing system as it is, with authors self-archiving in open access archives to expand open access beyond what is provided by library subscriptions. (I fully agree with both positions!).
So what does this have to do with Elsevier? Simple: Elsevier is "green" on open access and hence the darling of the green roaders. As long as Elsevier supports this approach, the open access archives first supporters are likely to support Elsevier. However, as we saw recently with the Research Works Act, Elsevier is quite capable of doing its best to attack the open access mandates that are critical to the green road. If Elsevier keeps up this attack on open access mandates, it's a matter of time the green roaders become gold and join us in the Elsevier boycott - where they will be most welcome!
So what are the options for Elsevier? They can either support - or at least not attack - the open access mandates that are coming, particularly the U.S.' FRPAA and the growing institutional open access mandates movement, and keep the support of the green roaders - or they can attack the mandates, and face a much more united open access movement. I think that this is what people like to call "between a rock and a hard place".
Of course, Elsevier could follow the lead of other major commercial scholarly publishers such as Springer, Wiley, Nature Publishing Group, and others, and aim to compete in the obviously emerging open access marketplace. This growing tendency towards OA competition is a topic that I speak to in a bit more depth in the 4th chapter of my draft dissertation, open access as solution to the enclosure of knowledge.