Microsoft's Nokia phone acquisition was an attempt to rescue Windows Phone through vertical integration. The deal transferred hardware capability and tens of thousands of employees, but a $7.6 billion impairment soon made the strategic failure explicit.
Facebook's Instagram purchase looked extravagant in 2012, but it bought a fast-growing mobile network at exactly the moment Facebook needed to prove it could win beyond the desktop.
Apple’s iPhone was a multi-year R&D and platform investment that combined hardware, software, carrier negotiation, and an application marketplace into a new software economy.
Google’s quiet 2005 Android acquisition bought a small mobile-software team that became the foundation of an open platform protecting Google’s services in the smartphone era.