I already had an account when Quora did it, and that made me use it less (wasn't always signed in, wasn't always willing to sign in - e.g. incognito sessions). For a long while, I started going back less and less - was only brought back occasionally by their emails which were still pretty good.

Recently the emails got so bad that I unsubscribed (I kinda expect to stop visiting the site completely). So I'm guessing I'm not alone in reducing my engagement - the quality of the whole site seems to have gone dramatically down.