[bigiain]

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).

[rdtsc]

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...?

[bigiain]

Two comments:

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…