Pinboard: How many users are using the service?
tl;dr Pinboard has 9550 users.
Pinboard charges a one-time signup fee of $9.55 for new members, the fee is based on the formula: number of users * $0.001, so the current number of users is $9.55 / $0.001 = 9550 users.
Reference: https://pinboard.in/help/fee/