Surprise! Facebook is using Office 365 now

Facebook's staff of 13,000 employees are now Microsoft Office 365 users, the social networking giant announced Tuesday.
"Do you want to know why we chose Office 365? It's because of Microsoft," Facebook CIO Tim Campos said in a video. "Microsoft got cool again."
This is a big customer win for Microsoft because tech companies are often the core domain of Google's productivity suite. The news comes as Google has been pushing harder to try and pick up enterprise customers from Microsoft with