I believe OP mens abusing market power to prevent competition.
Although if it is or not a monopoly and an abuse of market power is dubious, but it clearly is anti-competitive.
This is similar to Amazon shutting off Google Products from any retailers using its platform. It is anti-competitive, but the jury is out on whether it is abusing market power.
TL;DR: you can try to shut off your competitors from the market, as long as you're not abusing your market power to do so.
PS: The Hacker News definition of monopoly has nothing to do with the economics, policy and antitrust definition of monopoly.
How is it anticompetitive to stop sharing data you own with another business who has taken a more competitive stance against you? It’s not like Facebook is a public service that everyone is entitled to. And I say that as someone who deleted his own account long ago. I dislike Facebook for a lot of reasons but this isn’t one of them.
It is retaliation for another business competing with you. That is literally using your market power to try to reduce competition.
But taking anti-competitive actions by itself isn't necessarily an issue, but it is a problem if you're deemed to have significant market power in a defined market.
Essentially: if Facebook is deemed to have significant market power, this could be a problem, if it doesn't have, then it isn't a problem.
Anti-trust relies heavily on the precise definition of a market (which is a subject that Hacker News comments generally ignore when crying wolf, I mean, monopoly).
I don't think its anti-competitive considering they don't need to provide any third party APIs at all. Plus it's not like to create a social app you absolutely need FB login or FB data. I think if your company can't make it and you're blaming FB for not giving you enough data maybe your business model was a little too dependent on Facebook in the first place.
