In 2004, just as Apple's iPod was taking off and Google's stock increased 4x in price, Steve Ballmer posted a memo that outlined Microsoft's focus areas:

"Non-PC Consumer Electronics: The opportunity is virtually unlimited to integrate the richness and intelligence of the PC world with everyday devices such as mobile phones, handheld devices, home entertainment and TV. At the center of our efforts are products such as Pocket PC and Smartphone, Portable Media Center, MSTV, MSN TV, Windows Automotive, the Windows Media Center Extender, and other electronic devices built on Windows CE and Windows XP Embedded."

(Source: Ben Thompson)

When companies grow big, they inevitably lose focus. The more products you have, the harder it is to know what to focus on and when. Unlike Microsoft, however, as a startup you don't have nearly infinite resources to throw at problems. Your single advantage is the ability to press on one thing at a time.