Yahoo had brilliant mobile talent 2004-2008 - smart engineering and product talent that I remember meeting and they knew what was going on. But Yahoo management from 2007-2011 was terrible - ad execs overpaid with little clue about the tech world or what was happening outside their high castle. The second problem from which Yahoo never recovered was going HTML5. FB went HTML5 and the mobile product was a disaster. But FB quickly recognised that and went native - Yahoo took too long to fix issues like that. And the article is of course spot on about Tumblr - when they needed messaging they bought a blog platform.