When you operate on the scale of Amazon or under financial regulation like the other three, it pays to be on the government's good side. If you're merely an ISP or hosting provider that does email, your business doesn't need to interact with the feds much, so there's very little extra-legal leverage they can use against you if the necessity of a warrant is well-backed by the courts. In cases like that, you may have much more to fear from your clients than from the feds.