Dropbox has half a billion users, but it needs more paying businesses

Dropbox has long been an incredibly popular choice for cloud file storage and sync, and the company announced Monday it hit an important milestone: It has 500 million registered users. That number leaves out a lot of information. It's unclear whether Dropbox has 500 million unique people registered to use its service, or if it has 500 million registered accounts, with some people using multiple accounts. The company also didn't say how many of those accounts are active. Dropbox also sa