The ones with actual users
These are the sort of self-generating monopolies I've seen in the past 25 years of the internet.
Effectively, everyone goes there because everyone goes there.
A bit more than herd mentality, but makes any startup something which requires large amounts of energy to succeed and then keep going. Never stop.
Twitter has self-inflicted wounds, thanks Elon, but continues to limp along. I find myself less likely to visit because -- not everyone is there any more.
Not all Venture Capital are angels, some come in and kill the fledgling company and take it's IP, others wring it dry over months or years while skimming money off the top. Never occurs to some investors a company could be the next Alphabet or Meta.
This would then block the future as depicted in Minority Report.
"Hi there! Would you like to buy another [highly personal and embarrassing item]?"
There's a relief.
I visited Activision in the mid 1980s, when it was a shoe-string operation. Games for the C64 were coming along and quite impressive, including Little Computer People, which was running on a desk over a weekend to check for stability.
Seems it's all about IP these days.
They're coming for the upper bands which were available to Ham Radio enthusiasts. FCC doesn't care about us anymore.
The world is moving so fast these days that the man who says it can't be done is generally interrupted by someone doing it. -- E. Hubbard