This looks great but I'm not sure if the title is accurate. For most of the world the barrier to running an exchange is four fold:

1. Technology

2. Regulatory

3. Trust

4. Critical mass

This looks like it only address 1. Which is certainly a big hurdle but I would have loved to seen something explaining how to get 2 - 4 done.

From some of the answers bellow:

> You don't have to trust! 0x Exchanges are non-custodial

That's great. There should be a writeup on that front and center of the how and why.