Facebook serves the function of a common place where most people you are likely to know can be located. Want to know what your old friend from high-school has been doing the last 20 years? Is that girl you're crushing on single? Don't know any of your cousin's contact info?
Type their name in the box and it's probably there. No other service provides this functionality.
Sure Google might give a hit on the third page or so, but Facebook will limit the search to things like what schools you went to, where you live, contacts you have in common, and other Metadata tied to your names. And even if a viable, attractive, competitor arrived it would require billions of people to sign up and maintain multiple profiles. As people limited themselves to one service or the other, they would both be weakened by 'holes in the net.
Perhaps a third party that can search all of the subnets and merge them internally could solve the problem, indexing multiple platforms?
The way I see it, a 'universal global person locator' is an inevitable invention, and functions as a natural monopoly akin to a towns water supply. Facebook hit critical user mass first, and thus became the standard. This is the only problem with capitalism, the rich keeps buying up all the competitors. The government is just as fault. Because if they understood anything about technology they would know not to let these companies keep buying.
Facebook is easily the most evil among others by any measure. By design, they create a closed system where you can shop, communicate, get news, etc. all in one place and never leave. It's very easy to let them control 100% of what you see. Echo chambers are already bad, but when it changes your experience of reality, there's a whole different level of bad happening.
It is time for MySpace to rise up from the ashes 😁