As for the telephone conversations, read this thread a bit more... the government didn't need permission to wiretap until a specific law was passed in 1934 that required it.
Sure, Facebook/Google have more access than a bank has to the safety deposit box, but the likelihood that anyone at Google or Facebook has actual knowledge of the information the government is looking for is slim to none.
Maybe a better analogy would be a warehouse. Just because things are stored in the warehouse, and employees have access, doesn't mean that the employees have rifled through them.
The law should conform to what's best for society but you need to understand where the law is not best for society before you can understand where to change it.
The whole reason OP gave that the DOJ policy "makes sense" is because there's not actually 4th Amendment protection for this case. And he's right, so don't shoot the messenger, he's telling you what needs to be fixed in order to restore privacy controls closer to what we envision as ideal.
And that is important because a government that can affect things around the world does not run on "expectation", it runs on the law. You can complain until you're blue in the face about how the government is violating your expectation of privacy.... or you can fix the law, as was done in 1934, 1968, 1986, and many more times in between.