All that said, I think there is more room for the UI Developer role in a company that does lots of client work on a frequent basis (this person might work on 5-10 new projects each month), not so much in a startup or web application shop (4 months to a year in between projects/redesigns with a small amount of template and style work required for features after the initial work is completed). No hard evidence beyond my own experience to support this reasoning, but thought it was worth adding to my above points.

Cool. Agreed.

Good call, this does need better clarification. Thanks. I was aiming at the idea that a JS Dev will need to think through model relationships, views, security, performance, etc... (similar to what a "back-end" dev does)...but I could have phrased that better.