[onion2k]

That mitigates the risk of depending on services, but it introduces a huge new risk by committing development time to a feature that provides no value to the user and potentially, if the providers last, no value to the business either.

Any startup founder who follows this strategy is concentrating on the wrong thing. Pick the provider who's most likely to last and build against their service. That way you are more likely to fail than they are.

[taneq]

You're conflating "using an external product" with "using an external service". The third option is self-hosting a third-party product, which gives you the best of both worlds (reduced development cost and time, reduced risk due to continued reliance on third party).