We also noticed that users dislike the NASCAR-style plastering of branded login buttons. If the user recognizes none, she’s forced to use a new identity provider. If the user recognizes one, the others are distracting. If the user recognizes more than one, she’ll likely forget which one she used the first time, click another one the second time, fail to retrieve her data at the web site in question, groan, and start again.
I can never remember whether I had logged in with my Twitter or Facebook account whenever I revisit a website where I previously created an account. I switch back and forth between social networks with no clear reason other than the whim of the moment.
I do like it on mobile apps though especially since I hate creating new passwords without 1Password generating and saving the login credentials for me.