These google-docs-spinoffs are fun, except for one part: you lost me on the authentication.

Please please do not make me create another username/password combination; maintaining systematic password diversity is a high-cognitive task which imposes a barrier of entry to your app that's simply not worth it for me.

(I'm actually very agnostic of what drop-ins you use -openid, google auth, hell even facebook auth -just as long as it's something I can just click through (granted I'm logged in to those sites))