Roy Tennant writes that "Tags, ratings, and reviews should help enrich the whole, not one particular library catalog."
The problem is (after convincing TPTB that tags etc really do enrich the catalogue) how to get the data from one library to another. We're not really set up to share metadata like this with each other. --Uh, no, wait a minute. Isn't sharing metadata what copy-cataloguing is all about?
What if we simply (went through a huge bureaucratic decision-making process and) created some new MARC fields for tags, ratings, and reviews?
Then it'd be (a programming nightmare to allow customers to update these MARC fields and then to allow libraries to update to and from the network, but otherwise) dead simple to share tags, ratings and reviews with other libraries through the standard metadata-sharing networks.