Mark Zuckerberg: Our Biggest Mistake Was Betting Too Much On HTML5
Supporting clues:
But facebook haven’t given up HTML 5. [Quora Thread]
Future of HTML5 [Zhihu Thread] [CNET]
Other post:
http://www.theregister.co.uk/2012/09/14/facebook_html_5_vs_native_apps/
http://www.sencha.com/blog/the-making-of-fastbook-an-html5-love-story
http://www.businessinsider.com/bii-report-why-facebook-defriended-html5-for-now-2012-9