> What is Tailscale getting that my ISP and google/Facebook via their pixels and tracking scripts aren't?

Tons more. A lot could be written about, but a few "for starters" things to think about:

    - The web is decentralised.  And a lot of the web trackability can be dealt with in a dozen different ways.  But Tailscale is centralised and all the data nicely structured (stable node keys etc.) and "ready to go" for metadata analysis.
    - Tailscale have "behind the firewall" visibility at a far greater level, it enables building of a topology map and associated flows.
    - Tailscale visibility is perhaps most concerning in relation to metadata surrounding mobile devices.  Where is the device ? Is it in use ? Is it near other devices (from the same customer / other customers) ? etc. etc. etc.

Yes, `--no-logs-no-support` exists for the Tailscale client — but that's per-device, per-platform inconsistent (as the docs show), forfeits support, and doesn't change the fact that coordination traffic, the DERP relays, and the control plane still run through Tailscale. You can't opt out of the centralized control plane at all.