The problem is that businesses don't always have a choice. Maybe big corporations do, but for small companies, you have to deal with that the locals ISPs give you. Where I live (Italy), unless you happen to live in a major city (and even there, the coverage is small and the best speed you can get is 10mb/s) the best you can get is a SHDSL line, which gives you at most 8mb/s for about 300-400€/month. And that's if you're lucky to have a central nearby that supports it, otherwise ADSL2+ it is (1mb/s). I'm sure this is the situation in most of the world.

There's is also the "political" problem (as outlined by everyone else), I can't see every company wanting to outsource the storage of their secret data. Then you're also at the mercy of Amazon, that for whatever reason can stop providing you service (It's a tiny possibility, but it's still there).