I think you need to gain some perspective. They just didn't respond to your email. It happens. Fwict, it was outside of the expected communication channels for proposals anyway. It would have been more respectful if they contacted you, I can understand your frustration waiting for the reply, but you've completely overreacted. IMO what's most unprofessional about the incident is you taking such a minor grievance to a public forum.

I don't see where they exploited you. I'm not familiar with how elance works but it sounds like you submitted a proposal and never heard back. That's pretty standard in my experience.