I noticed on my site that majority of people who use FB to register also like to set their own username (and not use the default firstname.lastname username from FB).

Small feature request:

When user registers with FB/twitter/google, just show them three textbox to enter values:

1. username

2. display name (if enabled)

3. Password and confirm password.

We can have the username and display name automatically filled from FB/twitter/google username.

Let user select these three things before they actually register on the forum. I think they would like that better than been forced to use the default username (which cannot be changed once they register). Maybe add in security question and answer too.

Sorry but i disagree, thats not what SSO is about. The reason for sso is that you don't have to fill out extra forms. The whole process should be easy and simple.

The user can change everything later (user name not directly but if you enable display name it is possible).

I mentioned because some forums only allow username to be shown (they disable display name). In this case the user is stuck with FB/Twitter/Google username.