I thought there was a legal requirement to have unsubscribe links that work? I was charitably assuming the unsubscribe function was broken by accident rather than by design. Furthermore, this tactic only works if the site has content interesting enough to overcome the extreme irritation that ignoring my attempts to unsubscribe: this is not only rare, but the site is shooting itself in the foot. There's no way I'd ever let a Quora app have access to my phone after pulling that kind of stunt.