[some_googler]

"the NSA/CIA could just have agents infiltrated at Google, to get access to a lot of that data" -- this would be really difficult, because no single person at Google can just sudo in some system and feast over sensitive data. Any access to user data or other highly sensitive data needs to go through a stack of authorizations, the granted access will be scoped, and we have obsessive amounts of logging in place even for trivial stuff let alone sensitive systems and data. One thing that surprised me with the Snowden leaks is that the NSA's "checks and balances" seems to be orders of magnitude inferior to what we have at Google; something like that is unimaginable here (esp. if you can believe the NSA in that they don't even know which documents were accessed). Even a conspiracy involving several infiltrated googlers at the right places couldn't do it without anyone noticing, because they'd need to sabotage code and configurations that live in repositories that thousands of engineers have access to (and have enforced code-review workflows); the internal openness of our systems is in fact among our best defenses against sabotage.