IBM was a much bigger and more domineering monopoly at it's peak - there was a time where you effectively could not have computers or a datacenter without paying IBM money, directly or indirectly. I wouldn't qualify most of the FAANGs as monopolies (at least not yet) - reasonable substitutes exists for all of them.

The modern market does favor a handful of large players for each market - this is true in almost all sectors though. This not a monopoly though; as long as the top players change over time it is still a working market.

To be a monopoly, your industry has to matter a lot. Except for part of the 90s, IBM’s dominance wasn’t that important relative to the world. Even with big tech not as monopolistic as IBM, I think they are far more influential now. Even individually.

> To be a monopoly, your industry has to matter a lot.

This is not a part of anyone's definition of 'monopoly', ever. Monopoly means dominance in a particular market - nothing more, nothing less: https://en.wikipedia.org/wiki/Monopoly

Some admittedly silly examples of monopolies that fit the definition you’re saying. I know some one on HN before posted a much better example. I can’t recall it now.

Foursquare’s Swarm has a monopoly on social network checking in to places with optional photos + logged notes.

Tiago Forte has dominance in courses/in depth, varied content on building a second brain.

Readwise.io has dominance in spaced repetition learning from synced data.

There’s only one or two sites/communities for my personality disorder that doesn’t get much attention. They dominate the market.

There’s only one app that has you put up money for habits/challenges you complete via video selfies. Spar App (side note: horrible ownership/stewards of the app)

There was previously one community forum for video game site owners.

[almost] all of these have [near] 100% of their market. I don’t believe people would consider any of them monopolies.