Cloud storage and file synchronization have become an essential part of many people’s lives, and Dropbox was one of the first services to offer those features. Even though technology giants like Google and Microsoft have released their own file hosting services in the years since Dropbox first launched, Dropbox has still managed to hold its own, and now has more than 500 million registered users, according to an official blog post on Monday. That’s definitely an impressive number, but it doesn’t mean much when only a fraction of those users are actually paying customers, which is something Dropbox needs to change if it wants to continue competing with the big kids.