There is something these companies allowed that went beyond others, Twitter is not listed for example. As Snowden pointed out [1], these companies need to make some kind of technical assurances for privacy, otherwise customers (and potential employees) should look elsewhere.

[1] "The [telcom] companies should write enforceable clauses into their terms, guaranteeing their clients that they are not being spied on. And they should include technical guarantees. If you could move even a single company to do such a thing, it would improve the security of global communications. And when this appears to not be feasible, you should consider starting one such company yourself."