A really interesting chart (see below). It turns out if you add up the three Yahoo! properties, that at 13.9% market share, it only trails Facebook in terms of providing a platform for sharing links and information online. If you factor in email (of which Y! has a large share as well), the share would be even higher. It goes to show that Y! is still a well used medium for connecting people online. The engagement is probably nowhere near as strong as Facebook or twitter, but given the assets Y! has (including Search and its media properties), over a period of time the link information can be syndicated and re-used in many different places to surface interesting content to users. Twitter and Facebook links tend to go stale and fall away, whereas Y! can re-use them to enhance search results, or to republish content in different places.
Link to the article here (thanks to James Bilefield for sharing it via Facebook & Twitter): http://www.businessinsider.com/chart-of-the-day-social-networking-sites-dominate-sharing-2009-7
The math(s):
Y! Bookmarks: 5.5%
delicious: 4.5%
Y! Buzz: 3.9%
Total Yahoo! = 13.9%
Good to see Y! Bookmarks/MyWeb still holding up well 
