Yahoo sold delicious 2 years ago: http://techcrunch.com/2011/04/27/yahoo-sells-delicious-to-yo...

And killed their social network about 4 years ago: http://en.wikipedia.org/wiki/Yahoo!_360°

And they tried a Facebook partnership that kinda went sour after Yahoo attacked them with patents last year: http://techcrunch.com/2012/07/06/yahoo-facebook-patent/