I've seen a number of cases when questions have been migrated from one site to another (SO-->SF, SO-->SU etc).
If the original asker doesn't have an account on the site to which the question has been migrated, he basically loses track of the question. This is especially true of questions that are migrated to SU which still needs a password having to do with The Return of the Jedi.
I suggest that once you have an account on one of the sites, you should also have an account in each of the sister sites so that you can easily keep track of all your questions that have been migrated.
Edit: I know you can link the accounts. I just think this should be automatic in order to reduce friction.