I should mention that, while I said above I agree about trying to avoid vendor lock-in as much as possible, there is additional consideration when talking about

I should mention that, while I said above I agree about trying to avoid vendor lock-in as much as possible, there is additional consideration when talking about government projects and especially classified projects. Even if your software and infrastruture setup is as vendor-agnostic as you can possibly be, you can only ever possibly migrate to another provider that actually has data centers certified to host classified data and connect to a classified network. Building that data center is at least as much of a bottleneck to a government agency trying to change cloud providers as the actual software migration is.