Volida, I agree that security is super important for any site storing business information. We use S3 as our storage backend but do a lot of work in the application to enforce permissions. For any paid account (starting at $19/month), you can enable HTTPS. For free accounts, all login traffic and account signup is over HTTPS but other traffic is done over HTTP.
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.