Why now? Barra says in a Facebook post that his lifestyle at Xiaomi has started to take a toll on him and his health. At the same time, he says Xiaomi has grown enough that it can continue to thrive without him. After some time off, he'll be "embarking on a new adventure back in Silicon Valley."

What about Xiaomi? Barra's departure undoubtedly raises questions about Xiaomi's health.

• Earlier this month, the company declined for the first time to release sale numbers, with CEO Lei Jung admitting the company grew too fast.
• Xiaomi's meteoric rise made it one of the most valuable private companies in the world, but whether it can continue to justify remains to be seen.
• The company has yet to make a meaningful dent in the U.S. market.

Samsung's Note 7 investigation

Samsung officially concludes that the faulty and exploding batteries in its Note 7 smartphones were due to flaws in the design and manufacturing of the batteries

The details: Specifically, Samsung blames a design flaw in the batteries from one its manufacturers, which caused short circuits. Its other manufacturer—which supplied the replacement batteries—had a welding defect that could lead to fires.

Next steps: Nevertheless, Samsung takes full responsibility and has devised a new 8-point testing plan for all lithium ion batteries in its devices.