I've looked at their website, thanks for the pointer, I think I'll have to give them a go for my personal backups now :)

As for the application to VPN, I can't see much of a difference to other trustworthy businesses to be honest, I think I missed something there - are you referring to the prepaid aspect?

Tarsnap is extremely up about what they're doing, how much it costs to use their service, and how it works.

What they are not doing is offering the service for free or some flat rate and then finding non-obvious exploitative ways to monetise their user base.

Tarsnap is just a boring utility that you pay for what you use. VPNs should be like that.

Isn’t that just a normal business then? You pay something, you get something.

One would wish but alas a common mode of business is that people who consider themselves users sign up to use some service which is presented to them as being free, when all the while that company's actual business model is monetising those users' info and habits in every conceivable way and the 'service' is just the bait to get people on the hook.