I am a newbie in openID. I spend a lot of time thinking what the best-practices are to give the user the choice, to login with various OpenID enabled accounts.
(I have
Yes, the user will have to login with both.
Also, anytime when user wishes he can choose to add logins to his profile and identify his/her other openIDs like Blogger, Facebook etc. If he has created different logins (in grombeestje's table user) with these accounts then he can either drop one of the local logins (in grombeestje's table user) with the app or merge them into one.