Agreed, plenty of decentralized systems exist. None have the convenience of, say, an Instagram. If ever a decentralized system becomes widespread it will not be because of it's decentralized nature but because it makes it easier for people to do the things they care about. Distrust in Facebook et al. is growing. There's this "back-to-the-roots" meme going around. And there's the NSA clusterfuck. Maybe the time is right to build a convenient system that covers just the basic usecases for most people?