Well dropbox is one of the sites banned on the corporate LAN so that rules that out. Think it’s also unencrypted on there too. Dropbox claim their engineers can’t see anything, but I bet they can when the feds ask 😉
Google T+C look just like standard Picasa etc. They have to be written like that so they can do stuff like use your content to display in albums to public or display your pics as promoted photos etc. (ie using your content for commercial gain). Ditto for the scanning of mails to use as input for their advertising. Not sure why that would be needed for Google Drive though.
Not used Google Drive as such, other than already having a few docs shared in Google Docs (which Google can’t really make much use out of), oh and something appeared on Android phone 2 days ago.
I trust Google more than Farcebook, but not by much.