The handful of connected real "rockstar" programmers don't need to scan job boards. One could be a completely awesome programmer at a company which does not realize his/her potential and could be looking for a new job. Of course, mentioning the word "rockstar" doesn't really mean anything if the pay/benefits are no different from average. My point is not every rockstar programmer has a fan-following, famous blog, and tons of open-source projects. Corollary, not every programmer with a fan-following, famous blog, and tons of open-source projects is a rockstar.
This is a problem with the term. 'Rockstar' has pretty strong connotations of fame and confidence. 'Rockstar toiling in obscurity' or 'underappreciated rockstar' are contradictions in terms.
I hate the term myself, except that it seems to indicate a certain cluelessness that may be exploitable.