I love Maciej and all of his body of work and I aim to give him many of my dollars in the future - but this is something I'm going to nitpick on.
The reason why I feel comfortable using Pinboard on a day to day has nothing to do with the fact that I've paid for it because it's just as fragile and likely to suddenly disappear. It has a high "hit-by-a-bus" factor.
It's because Maciej loudly proclaims his love for letting people export their data. That's it.
This actually occurred to me and kinda bothered me as well. I saw an example during the FBI raid outage when the site was down in the morning on the east coast and there were no updates because he was still asleep on the west coast.
I just saw a post on Twitter from him about this: http://twitter.com/Pinboard/status/144174085629427714: "pals of mine have agreed to wind down the site in an orderly way and open-source the code if something happens to me"
That being said, I would still keep fairly regularly back-ups. With export this great, there's no excuse (short of maybe getting monthly back-up dumps delivered by email).
You might also want to tone down the snark.