It's much easier to see how a blog could be used effectively for an independent organisation than for a section within a larger organisation.

I can see a lot of ways in which it might be convenient to use 2.0 for training/ support/ information/ discussion, particularly because it would be much easier to keep such resources up to date and responsive; but I'm bothered about how these will relate to the central CMS system and to each other. We may add links to CMS pages from our personal/ local pages, but there will not be links to our personal/ local pages from CMS, and searching on CMS will not find information posted on personal/ local pages. This makes it difficult to use 2.0 for important news, and users will therefore have to be asked to keep an eye on multiple resources.

Could we request links from relevant CMS pages to our blogs, etc.?

The VHL use of LibraryThing sounded interesting (it was too far away to see) - but readers who search on this will have to search separately on OLIS for anything VHL doesn't have. In a way this is retrograde, since the point of the single OLIS database is that one search will find every copy of an item that a reader can get access to, wherever it is held. And of course VHL's tags won't be available to other OLIS users. Much better to develop a tagging system on OLIS itself.

Is there a risk of fragmentation of information among too many resources - too many sites/pages with almost but not quite the same information, not all equally up to date, linking largely but not systematically to each other, so that searchers travel around a cat's cradle of metadata with no certainty of ever finding the data they are looking for?

I would happily trade in the serendipities of anarchy for some degree of consistency and quality control.