The NSA will burn you
Bruce Schneier nails it in his message to internet companies in The Atlantic:
Do you remember those old spy movies, when the higher ups in government decide that the mission is more important than the spy's life? It's going to be the same way with you. You might think that your friendly relationship with the government means that they're going to protect you, but they won't. The NSA doesn't care about you or your customers, and will burn you the moment it's convenient to do so.
It will be the same with you. There are lots more high-tech companies who have cooperated with the government. Most of those company names are somewhere in the thousands of documents that Edward Snowden took with him, and sooner or later they'll be released to the public. The NSA probably told you that your cooperation would forever remain secret, but they're sloppy. They'll put your company name on presentations delivered to thousands of people: government employees, contractors, probably even foreign nationals. If Snowden doesn't have a copy, the next whistleblower will.
This is why you have to fight. When it becomes public that the NSA has been hoovering up all of your users' communications and personal files, what's going to save you in the eyes of those users is whether or not you fought. Fighting will cost you money in the short term, but capitulating will cost you more in the long term.
Great stuff. I just wish there was a middle way between (perceived) tinfoil-hattery and the NSA-compliant world pretty much every on the Web currently inhabits.
Bonus: you've probably got a Facebook 'shadow profile' even if you've never had a Facebook account. Scary.