why participating in open source projects

Ref [1]
http://www.techworld.com.au/article/535206/15_hot_programming_trends_-_15_going_cold/?fp=4&fpid=6

Hot: GitHub

Not: Résumés

Sure, you could learn something by reading a puffed-up list of accomplishments that include vice president of the junior high chess club. But reading someone's actual code is so much richer and more instructive. Do they write good comments? Do they waste too much time breaking things into tiny classes that do little? Is there a real architecture with room for expansion? All these questions can be answered by a glimpse at some code.

This is why participating in open source projects is becoming more and more important for finding a job. Sharing the code from a proprietary project is hard, but open source code can go everywhere.