Hi article does not really address the point he makes in the title. Email is the best source of primary identity for web applications. If you are building a business application that people want, over 95% of the time people will give you valid email addresses. User are so much more valuable if you can market to them over time. It is very difficult to do this without at least an email address. Of course people can get disposable email accounts, this is just stating the obvious but still does not help at all in suggesting a better alternative for primary identity.