On the other hand, a quick straw-poll through my contact list - out of all my friends/colleagues who I'd guess have used (or even heard of) those languages, I don't think a single one of them has been "on the job market" in the last 4 or 5 years (they're all either comfortably long-term employed at their present gig, or they've been successfully running or partnering small consulting firms of their own).
That is where good headhunters come in. I don't have a linked in account, Facebook or google+, and am quite happy at my current job, yet get calls from google or other companies periodically. Still don't know how they find me out, I do go to conferences so maybe they buy lists of attendees...?
1) I'm guessing (by reading between the lines) that you also haven't "been on the job market", and haven't been plausibly tempted to "jump ship" to any language-purist position?
2) <cynical mode> Just because you haven't set up LinkedIn/FaceBook/Google+ profiles yourself, that doesn't mean they don't all have "shadow profiles" for you based of the social-graphs they've got where your colleagues/friends have "leaked" information about your existence to them and enabled them to infer skills/abilities from them… I don't _know_ that they sell data from "shadow profiles" to recruiters, but I do suspect there's enough money in tech recruitment to make it likely…