I registered with the very cool Facebook about 10 minutes ago. I use Twitter a lot so i decided to "initialize" the Twitter app on facebook.
In facebook i was asked to provide my Twitter username and password, so i assume it could impersonate me to get my Twitter data. It had unrestricted access at that point.
Now Facebook is COOL. Twitter is COOL. Integration through impersonation in this way is NOT. I have no idea what the facebook twitter client does with my username/password or what data it retrieves. It just clicked with me that every app that is developed will do this, each with the same issues.
OpenID integration would allow the app to request my data, point me to the OpenID authentication site, where i can choose what data to share. This way i control my credentials and also my data. It's also very, very easy.
What do you think?