HEY, Micro.blog and web standards
It is fun to compare HEY and Micro.blog. They both depend on open web standards on the backend. HEY depends on SMTP while Micro.blog depends on HTTPS/HTML. HEY wants to re-invent the end-user experience while Micro.blog provides a pretty much generic end-user experience. By turning the end-user experience upside down, HEY doesn’t rely on IMAP. This is where some people turns their back to HEY (there may be other reasons, though).