Chaos ensued globally this week when Facebook – and Facebook-owned WhatsApp and Instagram – went dark. That's because the world's biggest social media platform now reaches more than 3.5 billion people a month. In many places around the globe, these apps are literally a lifeline: many small businesses rely on Facebook to sell their products, families use WhatsApp to keep in touch, and young people are hooked on Instagram. Indeed, if nothing else this week's turmoil reveals the massive extent to which Facebook Inc. influences people's lives — and livelihoods. We take a look at where these three platforms are used most around the world.