The thing about "only weak password accounts have to be reclaimed" is impossible, as the passwords are stored as hashes. Therefore MtGox can't know if a password was weak or not. So actually everyone needs/needed to reclaim.
(not saying this is what is/should happen)
It's not quite impossible. They can start with the assumption that all passwords are week, then when you submit your password for the first time, it can do the hash to see if is the right password, + also check the strength of the password at that time (since you just gave them the plain text password).
If it was a strong password they could unlock the account, if is was week, keep it locked and redirect the user to a claim site.
