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.
Yahoo received special commendations from the EFF for it's fights to secure your privacy. I wonder if it a business strategy. "We seem to be losing market share so lets fight strongly for our users privacy and when it comes out we're doing it it will convince people to switch." Or is it just a company morality. And why aren't other companies acting in our interests in a similar manner?
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.
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.
What "backdoors" were revealed, may I ask? It's been known for years that Google makes user data available to law enforcement agencies when there's a warrant. They've been up front about this with their transparency reports. The only revelation here is that there are additional secret FISA requests they can't include in the reports. That sucks and shouldn't be happening, but users privacy isn't being compromised any more than it already was.
I think this is an excellent example of a meme outside the scope of Internet pop culture jokes. The idea that back doors exist has such wide appeal, and is so easy to believe, that few people ask for evidence beyond allegations. Skeptical remarks are disregarded. The confidence people have in their own extrapolations from a few words in a single deck of PowerPoint slides[1] is astonishing.
If you were the EFF would you refrain from signing when the outcome aligns to an acceptable result? I believe that this is a PR move, but I also believe this is not the moment to dismiss the effort.