I didn't know this. Although as a tech reporter I should have, I would argue that typical people are unaware of these kinds of architectural implications and that without obvious disclosure this design decision sort of takes advantage of users.

Customers are paying twice, for the service and for other people's data, and it shouldn't take a Hacker News-level understanding of technology for them to be aware of this fact. It feels icky and reminds me of when I found out that Dropbox was "sharing" my files with other users: http://paranoia.dubfire.net/2011/04/how-dropbox-sacrifices-u...