It's a big, scary barrier for startups, for innovation, and we're running the risk of creating data superpowers that can't be competed with. Some algorithms don't perform well until they have a threshold of data. When that threshold is attainable only by a company with XXX million users, you inherently get a system where only those companies can innovate on the most cutting edge in machine learning.
That's a bad thing for us, especially if we find those companies turning against us. Did Google start putting a liberal spin on search results to try to influence the election? We don't know! But we do know that they are using their position to manipulate ISIS recruitment, which means they aren't afraid to get their hands dirty with this kind of stuff. THERE IS NO OVERSIGHT! And you aren't going to get a search engine that can come close to competing with Google unless you can find a way to match their data volume before you have something competitive. It's a massive barrier.
Facebook is enjoying the same sort of entrenchment. I've switched away from Facebook, and now I've lost touch with a lot of friends. They are my friends, why can't I export them? Why can't I export the data that belongs to me, and use it in some open-source format that allows me to reap the benefits of all the work that I spent tracking them down inside of Facebook's private garden?
As a society, we need to start addressing these things, or we are going to end up with Internet giants that we don't have the means to get rid of, and that aren't at risk of being out-competed.