Vicki Davis, co-creator of the award winning Flat Classroom project, recently blogged here about problems with Google forms. She had a Google form removed without warning. She was tracking logins for a collaborative project with the form. Google has offered no explanation or apology for the removal.
Davis' researched the problem and found similar reports by others. Google's 'Terms of Service' explicitly says that users should NOT include userids and passwords in their documents. One of the people who commented on Davis' blog hypothesized that the problem stems from phishing campaigns. She suggests that removing documents with userids is one way that Google protects its users.
I believe that Google could protect its users and provide a much better service to its users by alerting them before removing their files. However, this does serve as a reminder to all of us.
The cloud is not foolproof. You should have a backup of you data. Don't rely on the magnanimity of a corporate entity to secure your data. They will not be up all night retyping your paper if it is lost.