"Twitter privacy madness" or "I'm losing my mind"

What a bizarre, bizarre day! Brushing over the huge problems presented to us by the unfortunate case of a simultaneous fire and flood (wtf?) which took chunks of the UK internet network out - subsequently making my employers unfairly look bad and send the call centre into meltdown, despite the problems being neither our fault or within our control - I'm more than a little confused by a little twitter "following" incident.

Mid-afternoon I noticed I had recieved a small handful of new twitter followers in the space of just a few minutes. This has happened a few times in recent weeks, usually an early clue that one's website is recieving a surge in traffic. Oddly though, this time I recognised one of the names.

The guy is a work colleague, but one I've never met, working in an office thousands of miles and half a dozen timezones away from where I'm sitting now. We'll call him "A". Unable to resist temptation, I sent "A" a quick mail to ask if he was following me because we work together, or because he'd visited my site, oblivious to our meatspace connection. The ridiculously coincidental nature of this episode wasn't passing me by!

"I had no idea you worked here. I followed you because you followed me first."

And then he went on to prove it, stating I'd followed him 90 minutes earlier in the day, at a time when I was firmly in a meeting, away from my (locked) PC and not playing with my iphone.

OK, so now I'm confused. I went racing round twitter's settings and no, there is nothing there about 'auto-following' people, nor is there anything like that in the facebook twitter app or twitterrific. So who is deciding who I follow on my behalf? Is it a bug? Does someone have my password? Or is there something more sinister going on? I'll be very happy to be shown that there is a nice, easy, non-invasive explanation for all this. Anyone? Please?

As for my new twitter followers, don't worry, those looking for Web 2.0 insight get very bored of tales of my son filling his nappy, my wife burning salads or how much I am enjoying Match of the Day, and will soon leave in favour of those who publish worthwhile content. But it's nice to know you're there.