You forgot the obvious one: Google's secret robot army is unleashed and enslaves humanity. I find this possibility to be as valid as some of the ones you list. It could happen, sure, but Google ultimately cannot risk alienating their customers so they wouldn't do it. Even at Microsoft's peak the doomsday scenarios never came to fruition for the same reason. The first time Google does anything unsavory with the data they collect is the moment when they open the flood gates for their competitors to rush in.

I do think there's some value in keeping information offline and people should consider that as a valid alternative. You don't really need to account for every second of your life in Google Calendar. You don't need to upload every single photograph you've ever taken. You don't need to geotag the photos you do choose to upload. You may not want to use Google Docs to store your bank account information. Part of this whole situation is consumers protecting themselves.