As Gabriel mentioned in the blog post - "Identify people that would make good mentors, i.e. with the right domain experience." The site looks very generic from outside and forces me to signup without even giving me a peek of kind of people I can expect to see in the community.
I might be looking for a startup mentor in a particular domain, and may be there is none of that type on it right now. Or may be some people on it are providing mentor-ship on how to go about learning a specific skill like flying etc that I am interested in, but since I have no clue, I probably won't sign up.
You can think of highlighting a few profiles or at least a few categories helping a visitor understand whether (s)he should join this community or not.
Good luck, and hope it becomes a good success.