It's really not comparable though... It took Yahoo six years to earn the right to communicate about one particular lawsuit[1]. We have no idea how many legal challenges Google, Apple, and others are involved in but prevented from talking about.
[1] https://www.eff.org/deeplinks/2013/07/yahoo-fight-for-users-...
a) If a company is approached by any spooky three-letter agency, the higher-ups of that company could possibly interpret that as a validation that they've made it 'big' -- and furthermore, they could see in that offer a security that three-letter agencies then have an interest in seeing the company continue to scale up and succeed (because of limited funds, three-lettered agencies can't just go merrily creating tools that work properly with the 'next facebook' every other 9 months... and furthermore, there's no knowing if they'll come across resistance when they solicit 'direct access' to the next company. Also, NSA would have just loved it if China and Russia was a big user of Facebook... so I can even imagine them doing something subtle to try to make that a reality).
b) I have worked in the defense industry, but what I worked on was pretty unremarkable (and not at all weird). Most of my coworkers and bosses were pretty liberal. I remember once I asked my boss (with whom I was pretty close and friendly with) how he felt that he was working for the defense given his political beliefs... and he had a 'meh, gotta put food on the plate for my kids somehow' answer. Then he further reaffirmed that what we were doing wasn't anything special, it's the folks in the NSA who're doing crazy Stuxnet-type shit. If we weren't doing what we were doing, someone else would have. So, my point in saying this is, for all the rage you see on HN I really just can't help but wonder if these folks would deny an offer from a company who's working for the American defense. I really think the only reason there was a lot of commotion (finally) over this issue was that it had just the right PR elements: a good looking guy, leaving the country in a coolass way, humiliating the world power by escaping arrest, etc. I mean, anyone who knew anything about anything already knew about these programs -- this was the cover of Wired last year: http://i.imgur.com/3Rjh1la.jpg
Lastly, I think folks who're pretty made at the top leading will just acquiesce to requests from NSA for reasons mentioned in point a, and because folks at the top are usually the sort of people who care about succeeding and making a company profit as much as it can, they generally don't give a damn about anyone's privacy:
Zuck: Yeah so if you ever need info about anyone at Harvard
Zuck: Just ask.
Zuck: I have over 4,000 emails, pictures, addresses, SNS
[Redacted Friend's Name]: What? How'd you manage that one?
Zuck: People just submitted it.
Zuck: I don't know why.
Zuck: They "trust me"
Zuck: Dumb fucks.
http://www.businessinsider.com/well-these-new-zuckerberg-ims...
Think about other instances in which the U.S. government "forces" companies into doing things: say a new EPA reg or a new SEC reg. Every such activity is met with a flood of litigation from the companies affected. But here, apparently only Yahoo put up a fight.
It might seem like the DOJ is omnipotent, but really, it's a very budget-constrained and capacity-constrained entity (it's too busy fighting Nancy Reagan's drug war). People need to get their stories consistent on this point: if the government is owned by big evil corporations with lots of money, well the tech industry has plenty of those that can throw their weight and money around.
To be fair, I don't know all of the details, but my gut feeling is that if these companies had wanted to, they could have at least forced the DOJ to spend a lot of money and time getting their cooperation. As a practical matter, not doing so might have been the wrong move even from a business standpoint--each company possibly stands to lose a lot more than they would have had to spend on enough litigation to ruin the DOJ's day.