I suppose if I were to undertake it, all I would need is time (i.e., some savings) to produce a rough first version. To really build it, the help of other engineers on the back-end, especially to implement job matching algorithms. I'm mostly into UI.

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.