I've always thought of cloudflare as a plan to centralize the traffic that is not large enough to warrant their own CDN. All the examples you mentioned run their own content delivery in some way.

IMO cloudflare represents the death of the small player on the public internet, before it most small players ran their own internet-facing services, with it many choose to just run behind cloudflare.

In public policy, a plan that only the rich can buy their way out of is generally frowned upon by the Left.

Is the most relevant metric bandwidth, page views, or websites?

They may not have the bandwidth as you point out, but they have a pretty big chunk of websites. (Obv not 100%)

(That said, AWS has a lot more than “just” the TLS connection on a large fraction of the web, including all of my web properties, so yeah, who are you going to trust and for how long?)

Bandwidth is useful because it most directly corresponds to deployed physical hardware. If other providers have made that capital investment, taking customers away from Cloudflare is a matter of gradually rolling out features to meet their needs. Not trying to trivialize the effort, but it seems doable.

That’s not actually true. Compute cycles would be the best proxy for deployed hardware. Just delivering bits doesn’t actually take much hardware. (And not even sure why the amount of deployed hardware is a great metric.)

We specifically aren’t interested in pure bit delivery. It’s a commodity business that will have its margins squeezed to zero over time. We provide CDN services because caching is a useful tool in computer science when you want to deliver performance for other applications. If you measured our revenue per bit delivered, it would be far more attractive than any of the traditional CDN providers because we aren’t primarily selling bit delivery where they primarily are.

I don't think they'll actually manage to take 100% of the market, but if they take some big chunk they could still do a lot more damage than Google when they decide to start selling all free tier data or something (or even when they get an order from a future government to start doing something sketchy with traffic on their network, if that's more of a threat you're worried about; remember, they can see inside your TLS).

And you don't really have the option of switching CDNs (at least, not easily) if you've bought into all their proprietary stuff like their workers implementation, various optimization techniques that your site couldn't survive without, etc.