I wish I had the resources to build a competitor centered around openness and UX. It should monetize on really strong programmatic job matching, driven by the improved data from reducing all the UX friction. Somebody, please accept the challenge.
Getting users would be a whole other challenge. I can see the web/tech crowd adopting something for its superior UX, but then you're up against Github, which provides far more utilitarian value and accomplishes a bit of the professional social networking in one fell swoop. When it comes to everybody else, I think that business partnerships, marketing, and sales are key. That's more help needed.
I think it's totally viable, I'm just not in the position to do it. I hope somebody is.