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.
I guess you could argue that it’s different with crypto because your data is safer, but facebook has a billion users, and the people who’ve been doing the whole #deletefacebook thing, just signed up for Instagram instead. People really don’t care.
Would you sell your data for $5 a month? Maybe $15? I wouldn’t, especially not if it took time to setup and maintain, and I have a gmail account.
The reason I willingly give my data to google by using gmail is that they give me an easy to use cloud mail with decent spamfilters. Or in other words, they are saving me time.
Maybe you could offer me something other than money? Like financial statistics on how I use my money? Sure, but those apps are already here, and people are willingly giving away their data without privacy in those.
So you see, it’s not that I don’t think you can’t convince people to give up their data, I absolutely do think that you can, I just don’t think petty cash and privacy are good motivators.
Also I think the reason you willingly give data to Google for Gmail is that you don't have a choice. It's take-it-all, the spam filters and the data mining, or leave it and use ProtonMail, no in-between.
Your personal data has a cash value only because it can be used to influence future purchasing decisions. It's a simple equation, $x worth of personal data has a y% chance of generating sales worth >$x. It therefore stands to reason that the market value of the personal data of a person who doesn't have as much purchasing power will be less, and may not even cover the cost of stealing and then processing it.
Would you also sell your data for $3 a year?
What kind really? Here's the thing many people touting blockchain forget things like cryptographically secured messengers are not the "must-have" of an average Joe. Is it easy to use and can I talk to my friends? These are the only two things matter. Blockchain, for better or worse, has made things even more cumbersome to use. You have people relying on good-old physically secured hard wallets or paper to secure their keys. This is not a sign of progress.
And frankly about selling your data for money. I think people will find it easier to have some utility like free email or apps in exchange than money through blockchain.
When people talk about combining AI and Blockchain that's very often the exact problem they think Blockchain can tackle: programmatic transfer of value, so as to systematically compensate the data providers, in ways and quantities that'd be inconvenient to deal with otherwise. I won't bother finding a buyer for my car's windshield data if all that brings me is 50 cents a month. But if data from all my various devices can get me 100 bucks a month, and the set up and maintenance for the system is automated and trivial, I'm very likely to take the free money.
The second aspect is that you don't need to provide your data to the whole network, simply to those who compensate you. Not everything needs to be on the blockchain.
Thirdly, efforts are made into developing techniques that allow users to provide data for training, while keeping the identifying aspects, or even the whole data, private, either with simple k-anonymization or techniques that distribute the AI training part (Enigma does this iirc).
Don't get stuck on the "blockchain as a database" part. What people are excited about is a whole field of cryptography and trustless decentralized networks.