Launched in 2004, Google's web-based mail service has over a billion users. Many are getting closer to using up their free 15GB of storage, partly due to sharing the trillion plus images taken each year, not to mention 4K videos. And many users don't want to lose their email addresses or the archived email messages they have, so they will start paying Google for extra storage. This will add billions of dollars to the tech behemoth's bulging coffers and draw users away from other cloud services.