It even doesn't have to be a serious scam like taking something from you - money or your account (even that it is theoretically possible if the mail you wrote in the questionnaire is your SE account mail, so they will know your characters and the associated e-mail).
Enough that some random person makes a base of FFXIV characters and associated e-mails, sells it to adv companies or uses by themselves to annoy you with more commercial spam.