Microsoft so far hasn't released any data about Surface sales, feeding speculation that the device isn't faring well against the iPad or competing tablets that run on Google Inc.

NPR: Earnings Preview: Focus On PCs In Microsoft's 3Q

These issues, plus the fact that mobile devices are sometimes not able to connect and access content in the cloud, is feeding the already fast growing external storage device market.

FORBES: Changing Digital Storage Requirements for Clouds and Mobile Devices