I have the same concern about link sharing and more broadly information sharing for many years. I came across some social bookmark sites, such as del.icio.us, diigo, Pinboard, etc. Although some of them has millions users, tagging and stack are still not easy to use.
So I worked out my own solution based on the research and investigation on this domain for a long time. Right now, I'm reading the book from David Siegel: Pull - The Power of the Semantic Web to Transform Your Business. It covers various aspects of how to make web a meaningful community with common standards.
However, lots of previous efforts are not that successful, due to the difficulties for the industry to accept one standard. For example, in the book publishing industry, publishers, distributors and retailers all have their own catalog structures. When librarians want to classified all the books into a standard catalog, they failed again.
This told me that never pursue a common and standard catalog for any industry, just like the fact that there is no common product SKU list for the UPC classification. As long as we can organize the information in a de facto format to meet user needs, it should be good to go.
So I've published the beta site BingoBo.com for people to comment and have free trial. If you are interested in it, you can get more information from the Kickstarter project here: http://kck.st/JNqv8z, my blog site: http://bingobo.info or contact me at danmark.clara _at_ yahoo.com.