But what data? All of it or some subset? Aggregated, differentially privatised, non-identifiable chunks?

Without specific explanations, you could always weasel out of vague promises.

Sorry to sound negative. I'd love a service like this, but there's a very high bar for responsible implementation (in my opinion) and VC seems very unlikely to be compatible with responsibility.

Basically, what is your business model? Are you only making money from subscriptions, or through other means? What are the VC's expectations?