Potential UX issues with password-less logins?

There is a fantastic article entitled Is it time for password-less login? that suggests that we could use the "reset password" link as the default login action to any site. It provides a lot of benefits, such as not having to remember any arcane passwords and potentially increasing the security of the site, so in general I like the idea.

I can think of one issue, the unfamiliarity of the interface, but what other obstacles could a password-less login system pose to users?