I always wondered the same about ZeroTier. If the controller is under foreign control, isn’t the whole network compromised?

There are often some “fair use” paragraphs in their respective ToS that they could enforce and either terminate your account or request you to uprade to a higher tier product. Usually (not always) VPSs are overprovisioned, so when people start to fully utilize their rented machines theit whole business model goes belly-up.

Be careful with compute intensive tasks. Some providers don’t like when you actually utilize your rented hosts.