EDIT: the absolute graph is described as "percentage of matching job postings" so it's absolute (total number of jobs), but still "relative" to "other" job titles. so theoretically, one explanation could be that the economy was recovering faster on the tech industry, but now other sectors are catching up... (just a thought, not sure I'm even convinced, but still worth checking).
EDIT2: Seems that a clearly defined crash is not what most recruiters think about for 2013: http://media.dice.com/report/december-2012-special-edition-h...
I think its an interesting way to drive traffic to the site. A variation on the "does this house from your neighborhood look like its worth a million bucks?" kinds of things I've seen Realtors do.
Any serious analysis of the health of the STEM job market would have to be a bit more rigorous than a text match search.
Let's assume that there's 10,000 total job postings in your graph. If the "rock star" trend grew from just 1 posting to just 70 postings, that would represent a 7000% growth over the period, even though "rock star" would still represent just .007 of the total market.
Growth graphs answer a very specific kind of question, and it's rarely the question that people mean to ask.
Or, put another way: click the "Absolute" link next to "Scale", under "engineer, programming, engineering, rock star Job Trends".