The difference is awareness. Everyone is aware that there are radiowaves flying everywhere that could one day give us cancer. Everyone is aware when they're using a cloud based email that it's on the internet. If they're not then shame on them, because the information is readily available. If said email provider is snooping on emails without informing, well then shame on them in the same way shame on the Gov for this. It's about making the people aware or not explicitly attempting to hide it.
