We haven't given out unlimited as default for a few years now, but we always allow users to request more disk space and as long as the account is complying with ToS we bump the amount up if the initial requirements are met (account at least 7 days old, have a working site and use at least 50% of initial space). This was a decision made to combat abuse, some actually used our service to store illegally acquired copies of movies and tvshows as well as personal backups which is all prohibited by ToS.
Given the age of your account I'm fairly sure it would have been created with 512 mb initial limit, though there is a slight possibility it had 1 gb initially.
Since you meet the requirements I have bumped you to 1 gb. Should you find that you come close to using up that space just make a request here at the forums and we'll verify you are eligible for another update and bump it again.
