Look at companies like Uber, Whats-app, Dropbox, Snapchat, Instagram...these aren't flashes in the pan, but are ecosystems harnessing hundreds of millions of people. These companies are creating entire infrastructures and industries. Facebook, Twitter and Instagram pretty created the entire mobile advertising market. Uber is revolutionizing transportation.
Not long ago did MSN, Y! Chat, AIM boast multi-million people network. I wonder what makes WhatsApp, and Instagram different? One product businesses are also one trick ponies. WhatsApp has real ubiquity about them... (Replacing SMS), but then, I'm not so sure about Instagram and Twitter. Sure the celebs pull in a lot of users, but if the past is any indicator, social networks can come down in a heap...