I noticed RichB's thoughtful Thoughts on Bookmarks blog - you don't need to wait for Google labs to solve this, just use Google search "collaborative bookmark" and you can see the wealth of work that's already been done in this space! I agree with Rich that one valuable feature of shared bookmarks is the fact that they are maintained by a group, but I think a collaborative bookmarking system can have some other equally useful attributes:

• bookmarks can be checked regularly for update or availability by a network server
• each bookmark may be linked at multiple nodes in a taxonomy, or even in multiple discrete taxonomies
• you could subscribe to be notified to changes in specific taxonomies or categories
• if the structure of the taxonomic hierarchy is a separate entity, it can easily be shared which has two benefits:
  • users don't have to learn multiple taxonomic structures and the labels for folders in the hierarchy
  • a user could create a federated view of multiple taxonomies by a subscription mechanism; this would allow you to subscribe to a shared bookmark taxonomy with folks who have similar interests or a compatible way of classifying bookmarks
• could be capable of associating a title, description and keywords with a URL (the network effect of sharing a URL encourages the user to provide more detail)

A collaborative bookmark manager would complement the linking style of blogging nicely; blogs are great for providing topical links that have a short half-life, whereas a shared bookmarking tool would help to create more long-term value.

I think such a tool could have a natural fit with content management systems (CMS); instead of persisting transient web content to your own hard disk, you could request that a web-addressable page or document would be cached in your group's CMS (subject to legal limitations on storage due to content licensing). If you access a bookmark via the bookmark server, it could automatically redirect to the local cache.

Naturally there are issues of importing and synchronising bookmarks from existing end-user tools such as Mozilla or IE, but none of that is rocket science. It would also be desirable to be able to sync with public bookmark taxonomies like the DMOZ Open Directory; that could be helped if DMOZ exposed an RSS interface to complement it's HTML one.

Of course, RSS is a pretty effective way to expose the structure, content or updates of any collaborative bookmark taxonomy.

Follow-up: RichB comments that he was really thinking about a personal bookmark manager, but given his stated issues (1. the time it takes each person to setup this set of bookmarks that can help them with their day to day work. 2. knowing what that magic set of best bookmarks are.), I don't see an ideal solution for an individual. However if an individual's bookmark taxonomy had some structure (categories or folders) in common with a shared bookmark source, it would be possible to merge selected categories/folders of the shared bookmarks, either dynamically or a one-time static merge.