as i said once in a thread simileir to this:
basically they sent the emails to those who quited XIV in the first few months during 1.0 thats why the Alpha mails were sent to them instead of the majorty of the active players they wanna atract those people and pull them into 2.0 knowing that the active players wont quit 2.0 in the few months of its release. and yes some of those active players also got an invite to alpha and not to mention that the alpha started first in japan and then the rest of the world not to mention the stabilty of the alpha servers also which yoshi-p clearly stated that if the servers were to be able to have more players they will send more invites.
be cool the end of the world isnt 21/12/2012 and you might have a chance to play beta which is more better than alpha.
on a side note:
two of my friends registred at the same time exact day month year one of them got an invite the other didnt so its ok man.