I've noticed in the last week that a couple of these networks are "coming back at me" - and not always in a desirable direction.
It looks as if LinkedIn are starting to recruit people to take part in surveys. This is just about OK in my book - and at least they had the decency to ask if I wanted to take part in future surveys, and how often. Plus there was the option of donating the €5 incentive to charity.
But a worrying development happened via a site called InterNations, that I joined once, never used, and don't seem to be able to extricate myself from. It was a classic cold-caller selling financial advice who used every repugnant trick in the book until I called his bluff and he admitted to having my details from InterNations. What's rubbish about this, apart from the annoyance, is that not only did the financial advice firm take a plummet in my estimation for using such shoddy tactics (I'm not naming names yet as I am giving them a chance to redeem themselves) but the whole grubby feeling also manages to rub off on InterNations.
What you'd call a lose-lose situation, I suppose.