After using the new extra fields feature in Contonti, which i think is great, i came across one problem.
You can delete standard fields from the user table, such as user_name. Not understanding how this worked at first I played around with it. But i created an extra field called user_name, i might have got a warning about this im not sure. Then after messing about I deleted all the extra fields and started again, in the process deleting the "user_name" field from the user table!! Not the greatest thing to do, but this was on a test database.
As i see it i dont think a user should be able to create new (extra) tables that are named the same as the standard fields such as user_name, user_email, user_gender, user_icq etc ... This would stop the deletion of "standard" fields that are needed. Obviously you dont want to stop users from deleted extra fields but checking them before creation would stop this problem.