Perhaps if one got their key off of the store before the e-mails were sent something was recorded and the e-mail got sent to only those that had not already gotten their key?
Nope. I got my e-mail, and I did use the key before hand. It might be that people have not signed up for the Stardock advertisement e-mails, or did and discontinued the service. Might also be in the spam folders, this of course is all speculation.
