None.<p>There are way too many tools that now rely on a forced login/auth/id as a control/lock-in/pseudo-secure mechanism whereas it is not required by the actual task at hand.<p>For some tasks, it is needed. For a huge amount of others and most of them, it's an invasive market/control/payment tool.
User/password.<p>Incidentally, there is a way to conduct a poll in HN:<p><a href="https://news.ycombinator.com/newpoll" rel="nofollow">https://news.ycombinator.com/newpoll</a>