I discovered this by chance when I was sent a very confidential excel file which I could have sworn was password protected. On opening it with google docs, it openned automagically without asking for a password! Gasp!
I immediately called the sender and asked him to password protect the document but he insisted it was password protected.
There I was accusing someone else and thinking to myself it cant have been google docs. I mean its Google!!!
Upon downloading the original attachment I realized that it was actuaally password protected!!! Guess google docs have a way of bypassing passwords on password protected documents and that got me thinking how google has made life easier for prying eyes.

