i can't speak for the original poster, but often times rental chains get their dvds weeks in advance and employees are allowed to rent them in advance so they can better serve their customers when the movies are released.

that being said, i often backup my prestreets if i plan on buying a copy when the film does come out.

i'm not sure where that falls as far as legalities and the strictness of rules in this forum, but often times it's the video store employees you can partially thank for getting IFO files to slysoft and having an update for everyone else by the release date of the movie!