The so-called Darien Statement can be found at http://www.blyberg.net/2009/04/03/the-darien-statements-on-the-library-and-librarians/. I'm going to express a few of my thoughts here. There are some areas where the statement bothers me.
The statement is released under a Creative Commons Attribution 3.0 Unported license. The statement of responsibility indicated in the relevant blog post indicates that John Blyberg, Kathryn Greenhill, and Cindi Trainor came up with this. I'm going to restate some of it here. I will attempt to interleave replies.
"The purpose of the Library is to preserve the integrity of civilization."
How does that square with enabling legislation in most cases? Public libraries are public institutions and normally are creatures of statute. Libraries can only do what is authorized by statute. I imagine that the integrity of civilization is not something allocated as a responsibility of libraries in enabling legislation.
"The Library has a moral obligation to adhere to its purpose despite social, economic, environmental, or political influences. The purpose of the Library will never change."
History has shown instead that the purpose of the library has in fact changed. With the rise of "third space" theory and more, libraries have shifted in focus from being only storehouses to additionally being commons.
"The Library is infinite in its capacity to contain, connect and disseminate knowledge; librarians are human and ephemeral, therefore we must work together to ensure the Library’s permanence."
How this can be read depends upon your definition of "The Library". As for that definition, there seem to be multiple possibilities.
"Individual libraries serve the mission of their parent institution or governing body, but the purpose of the Library overrides that mission when the two come into conflict."
That cannot happen in a public institution. Insubordination is a firing offense in most government bureaucracies and librarians generally do not have tenure protections that might insulate them in these cases. There are normally only two choices when faced with instructions you cannot follow: resign or comply.
"Why we do things will not change, but how we do them will."
Over time, the "why" does change. LCSH was arbitrary until Lois May Chan was contracted to study its systemization. We still assign subject headings, but the reasons underlying those headings and our choices are different now compared to thirty years ago.
"A clear understanding of the Library’s purpose, its role, and the role of librarians is essential to the preservation of the Library."
I would think effective public communication would be more essential as the Nebraska video game case showed. If people had communicated, that whole mess would likely not have happened. Without keeping lines of communications open, taxpayers and those who oversee libraries are likely not to care about the library's role and instead prefer to cut budgets for better favored pet projects.
There is more to the statement but I won't address that at this time. In the end, it reflects a view of professional practice I've rarely encountered. What the statement aspires to seems to not be the norm in the US.