Dear Maciej Ceglowski: You're doing it right.
It is quite a breath of fresh air to see someone who's built a product, marketed it to the right audience, charged money from the outset (and thus not falling into the "users first, money later" trap).
I signed up for Pinboard (just out of curiosity, and wanting to see if my shiny new credit card did USD payments) pretty much the same day it was launched on Hacker News, and it became the first ever online service I paid money for. A mammoth sum of ~$1.
And since then, for this one-time joining fee, Pinboard has continued to add numerous features -- both asked and un-asked for -- while stamping out bugs nearly as quickly as they were discovered. And because it was making money, there wasn't a need to slather it in advertising or the atrocious amounts of social gunk that seem to crawl across pretty much every "Web 2.0" site now.
The Pinboard blog sees some brilliantly detailed posts and insights on technology (both site- related and otherwise), the site itself offers a spartan, uncomplicated and flexible API, and now -- this is what motivated me to pen this screed down -- the database schema behind the site!
This is how quality products are built - the real secret sauce is the execution; the actual idea and technical implementation detail can be at any point in the simplicity-complexity spectrum. It really is quite awesome to see someone basically give you everything you need to clone their product/service. The level of confidence in your own execution and delivery capabilities underpinning such candour and openness is a refreshing departure from the current clusterfudge that is "intellectual property".
Once again Maciej, you're doing it right, and I thank you.