@Lyude I feel like this doesn't quite address what I was trying to get at - you say "we", but who are "we" (ie. the people who functionally control the network) exactly, how are they organized, and what prevents a hostile takeover of some sort? Is it just a central organization? If yes, what legal form does it have? How do you ensure that those in power of it are universally deemed trustworthy?

The problem with things like "a widely used messenger" is that it becomes an incredibly appealing target to co-opt, and so you're going to have to deal with a lot more attacks than eg. your typical FOSS software foundation - companies trying to bribe contributors, legal attempts at takeovers on technicalities, sabotage, disinformation campaigns, and so on. The network effect is not just a barrier to adoption, it's also a large organizational risk.

Even if all of the people in power within the organization are absolutely spotlessly 'clean' and perfect (and that's already hard to achieve in this context), you're going to keep getting harassed by people trying to exploit the bounty of a large and widely used centralized network - whether it be corporations, governments, overt fascists, or whatever else.

A very big part of the motivation for federated networks (or fully P2P networks, but those introduce even more technical challenges) is precisely to address this problem; by structuring the system such that no one party holds outsized control, nobody is such an appealing target, and trying to take over *all* parties involved is very impractical and expensive.

So if we can't rely on that - because the premise here is to not rely on federation - then how do we address that risk in practice?