Free is not a sustainable business model. Everyone knows this, especially those who lived through the dot-com bubble 15 years ago. Everyone, it seems, except for cloud storage investors. Billions of dollars have been poured into cloud storage companies that are giving away their product, with just a tiny sliver of their customer base actually paying for anything.
Offering a free version of your product is nothing new for technology companies, but those who are successful at using this model either give the customer a strong incentive to upgrade to a paid version, or they do as Google has done and create a massive audience that can then be sold to advertisers. The most popular and heavily-financed cloud storage companies do neither.