I've been tracking[1] the use of "passionate" in whoishiring threads, really getting out of control. It's now become one of the 10 most frequent terms used in posts.
Everything is on the rise that you're tracking. Which would make me believe there are just more job postings and for all I know the term passionate may actually be on a decline in how often it's use vs how many job listings are made.
[0] http://www.ryan-williams.net/hacker-news-hiring-trends/2014/...