Data about the world ("There is a granite formation here") & personal data ("I am interested in chairs") are two fundamentally different ways to look at this.

Data about the world ("There is a granite formation here") & personal data ("I am interested in chairs") are two fundamentally different ways to look at this. So far we've built companies off personal data. But it can really only be used for one thing -- ads. Hence the many adtech startups of dubious social good. If decentralized big data were to take off, I'd bet all my chips it will be because of data about the world, which enables fundamentally different, more interesting, and more productive use cases. And is bounded by utility instead of personal spending. Currently you have interested parties either self-generating data, or specialized companies compiling targeted data sets (usually on commission). What you don't have is diffuse, global datasets (e.g. geotagged temperature readings from every cell phone on the planet, right now). That starts to get interesting. The "hard" technical problem is the driver of homomorphic encryption. In order to truly own data, I can't allow copies to be made. But in order to make that data valuable, I have to allow arbitrary computation to be performed on it.