I think the numbers encompass all jobs within the region-- not just tech ones, as you seem to be implying. If you include all employment sectors, then there are plenty of fulltime workers earning less than $30k: 27 percent, according to the article.
I'm actually amazed that the number is that high -- I figured that even the "menial" jobs would have to pay more than that in that region. It's hard for me to imagine anyone surviving in Silicon Valley on less than $30K, but I suppose that's just a failure of my own imagination.