"We offer people an off-site backup at the cost of trusting a third party with their password."
Yes, this is my main point. People have to learn that they shouldn't be giving out passwords to just about anybody.
I think this guy in the comments here (http://blog.geeksphere.net/2012/09/27/response-to-dropmyemai...) made a pretty good point. Maybe you might want to answer his doubts there?