Well, that's OSCON. Perhaps it's different elsewhere? Turns out... nope. "But this trend is more than the subset of the industry that attends an open source conference," writes sjvn. "To get to the real heart of what’s hot in open source job circles, I talked to Shravan Goli, the president of job site Dice.
Goli said, “The rise of open source jobs is part of a broader trend. We’re seeing tremendous tech job growth everywhere.” According to Goli and the Dice job trends, the hot areas are cloud, especially OpenStack; Big Data, Hadoop in particular; and the LAMP stack (Linux, Apache, MySQL, PHP/Perl/Python). Other really hot areas include the Solr open source search engine and anything with mobile phones, especially Android. In short, he says, “The newer tech is hot, hot, hot and recruiters are swarming.”
The article has a bit more information about the most in-demand jobs. So if you weren't considering open source as a career path before... now you have hard evidence that this is where the opportunities are.