I always just assumed they were building some kind of logging software (“tail”scale), used Wireguard to connect hosts, and just kind of stopped there. Don’t get me wrong, Tailscale is a nice way to connect machines. It’s nice because Wireguard is nice.
> Update 2019-04-26: Based on a lot of positive feedback from people who read this blog post, I ended up starting a company that might be able to help you with your logs problems. We're building pipelines that are very similar to what's described here.
Update 2020-08-26:
Aha! Okay, for some reason this article is trending again, and I'd better provide an update on my update. We did implement parts of this design for use in our core product, which is now quite distinct from logs processing.
After investigating the "logs" market last year, we decided not to commercialize a logs processing service. The reason is that the characteristics we want our design to have: cheap, lightweight, simple, fast, and reliable - are all things you would expect from the low-cost provider in a market. The "logs processing" space is crowded with a lot of premium products that are fancy, feature-filled, etc, and reliable too, and thus able to charge a lot of money.
Instead, we built a minimalistic version of the above design for our internal use, collecting distributed telemetry about Tailscale connection success rates to help debug the network. Big companies can also use it to feed into their IDS and SIEM systems.
We considered open sourcing the logs services we built (since open source is where attributes like cheap, lightweight, etc tend to flourish) but we can't afford the support overhead right now for a product that is at best tangential to our main focus. Sorry! Hopefully someday.