Possibly the most excellent post we’ve read this year: 8 Reasons Users Don’t Fill Out Sign Up Forms. Every website owner or maintainer ought to be required to read it and pass a comprehension test afterwards.
Briefly, the point is that users avoid signing up to become a member of a site unless they absolutely have to. Call it, if you will, “social media fatigue“. Ten years ago, the web was yours just like your TV set, and the only time you had to sign up for anything was if you were buying something. Now you can’t click a mouse button without logging in with a nick and password. Who can remember them all? Why does it feel like getting married every time you just want to leave a quick note somewhere?