If you have Twitter and Reddit in mind then the first thing is to understand that both are largely irrelevant. At least Twitter has become the de facto platform

If you have Twitter and Reddit in mind then the first thing is to understand that both are largely irrelevant. At least Twitter has become the de facto platform for instant, short "press releases" but that's about it. So what happens to them or their APIs is not important and they are not powerful in any real sense. In comparison, Standard Oil was a real, powerful monopoly that controlled a key resource. In the "tech world", I'd say Google is the one that matters because it has become the gatekeeper of the Web and Google ranking is critically important.