Sign in w FB not working as expected

Alex. Just tested it and it was not working well. Just watched someone try to signin using Facebook. After they entered their facebook email and password they were directed to the page with the TOS but they were presented with a required username field. When they filled it in, and checked the TOS box (that worked well) they then got to a page saying that the username is in use or invalid and similar for their email. He then had to enter a username again and email and confirm email. Meanwhile at the top right I could see the signup button had changed to a "My Account" button.

The user again entered a username and email and confirm email, but again it was not accepted. When he clicked on the My account button it was clear that he was correctly signed in.

I doubled checked the settings and I noticed that in the User tab of Configuration that the field "Generate Username (Normal Registration only) was set to "No". I changed that to "yes" and tested it again. This time it worked as you predicted.

The only problem now is that the automatic usernames being generated are a fb string of numbers. Not at all friendly. Is there someway to have the username generated be something that sounds a bit more like a person? Perhaps some abbreviation of their first and last name.