Keep in mind - this is a PR move. None of these companies did anything before their backdoors were revealed. They are only writing this extremely-public press notice because they are getting called on their shenanigans.
And I'm not actually sure about their market share since their stock is remarkably steady over 5 years and has been steadily climbing since the middle of 2012.
Yahoo's commendation: https://www.eff.org/deeplinks/2013/07/yahoo-fight-for-users-...
Yahoo's stock: http://finance.yahoo.com/echarts?s=YHOO+Interactive#symbol=y...
I know look at the max length of Yahoo's stock and yes, it seems they have dropped quite a bit at points. Dec 1999 being their highest at 108 and change (dot com bust I'd imagine came shortly after), and as high as 39 in 2006 up from a low of 4.45 in Sep 2001. Currently 29 though so they've been putting in work since they dropped to 11.51 in Nov 2008.
1. Unless I've missed some crucial evidence