I am a very happy user of Pinboard. And thanks for posting stats! One things which looks worrying is the stagnation of the number of users. By a common social media wisdom, it's a very bad sign... but some time ago I did analyze MathOverflow community (a research-level mathematics Stack Overflow) and they saturated in the first months (sic!) http://meta.mathoverflow.net/questions/2182/is-mathoverflow-... , yet it is…
The number of daily signups and so on has been steady for years, I'm glad someone else is worried about it, so I don't have to be.