Hello, I've looked at Net::Google, and 90% of the modules use AuthSub with a mandatory login/password. The right way for a web application to interact with Google applications on behalf of a customer is to use OAuth. That way, the authentication is done by Google, and the application does not know the user's password. This is supported by Net::Google::DocumentsList for example.
Are you aware of modules that can work well with Picasa and Blogger, for example, using OAuth. The current Net::Google::PicasaWeb handles read-only queries, no add/remove/update actions.