It's also possible that DropBox is planning to get into the Cloud business, and views its customers as businesses that'll build apps on top of their DropBox shares rather than consumers who might use Carousel or Mailbox. They're already making more than Box among enterprise customers, and it's notoriously difficult to squeeze money out of consumers. And they're closer to the consumer than AWS or Google Cloud Services. The move to building their own datacenters makes a lot of sense in this context.