Meno,

>>how do i as an admin make it mandatory for users to chose their account type when they login using facebook, google or twitter?

I can tell only how this works with FB connect, since other plugins (twitter, google) were not developed by us.

If you are using FB connect, then user who loged in using FB account will be assigned a first account type from the list of all account types. Admin sets which type will be first in  Admin Panel>Profile Questions> Edit Account types ( use drag&drop to move account types up or down).

>>Also, how do they change their account type from their profile? the option is not there!

Users can not change their account types from their profiles.

Thank you for the answer, but i must admit that i'm disappointed by that.

Meno, why would you like users to be able to change their account type?

Well, for a very good reason. I am creating an online directory for talents, and you know there are many kinds of talents, i wanted to give each one of them the free will to choose what they are, like, Photographers, musicians.. etc
that way, each one will get questions has to do with their own field and each would have their 'type' shown on their profile for others.

I have almost the same question.

I´m the admin, and I want to change the account types.

This is important because we can create one profile for each type of user. Some questions will not be needed for some kind of users, and other questions are very important for any others.