Hiring from open-source

Reading Chris DiBona’s blog I found this interesting post on another blog.
Reduce the risk, hire from open source (Loud Thinking)

I think it makes some very interesting points.
Working on the WURFL project has taken a lot of my time, both working time and spare time. Sometimes most of my spare time and none of my working time.
I am sure this witnesses my passion into the project itself, programming and the mobile world.

Working in the WURFL project brought me some really interesting contacts, of course and hopefully this will be reflected in more opportunities in the future.
My current contract and the last 2 years of my working time have happened thanks to WURFL and the contacts that it generated.

Often the interview was really a few minutes and something like “We want to do this and that, can you do it?”.
Sometimes I was surprised by how quickly this happened and how people wasn’t really much interested in my CV. I think this also confirms how CV’s can sometimes not mean much (both on the good and the bad side).
I wonder how could you understand if someone is good at programming or has good analisys qualities in a 30 minutes interview.