Today, i suddenly could no longer log into minecraft, getting the message my account had migrated, and i needed to use an email adress. Fun fact: i was still running on a Ye Olde Account, logging in with my username yesterday. Needless to say i have no idea how i got migrated, or to what email... and mojang doesnt allow you to log in the oldfashioned way anymore.. Anyone have any tips on what to do now, apart from write to Mojang directly? Edit: after a lot of fussing about, i managed to get a copy of my buyers ID, and sent a regular migration request to mojang. I should be back before christmas!
Someone tried hacking my account last year, be prepared for the possibility Mojang's reply might take longer than anticipated due to the time of year. Hopefully they get back to you soon.