h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Now, I experienced something rather strange today... I can't quite figure out what actually happened, but it's worth telling anyhow.

I was in town (Drammen) today with a friend of mine, Kristian. We went into a bookstore, bought a couple of books (can't live without a fresh supply of reading material) and went into a CD-shop. Now, in that CD shop were two teenage girls, probably around 14-15 years. They were what we in Norwegian call "berter" (meaning teenage girls obsessed with fashion, with a huge and complicated social life involving loads of schemes against various "friends", they usually have a total lack of intellect and personality). Well, my friend went over to the CD rack and pointed out a CD he found totally pathetic ("The sound of snow"), and the girls immediately started giggling. That was not unexpected, at least I expected that because I'm a "weird" guy in their eyes. But what happened next was _very_ unexpected. Those two girls followed us around for 20 minutes, always a couple of steps behind us, thinking we wouldn't notice. They followed us into five shops, some of which we went into just to see if they were really following us (two teenage girls in a shop selling computer games is _very_ unusual). They watched us the whole time, always snooping in on our conversations... Lastly, we went into a kiosk to buy some ice cream, Kristian was getting paranoid by now, but they seemed to have left us at last, because they didn't come into the kiosk. But when we came out, they were waiting for us outside the kiosk, with a camera. They photographed us, and then they ran off. We didn't see them again, and I really don't know what they were up to...
It's about the strangest thing I've experienced in some years. And I've seen a lot of weird things. So I'm wondering, what do you think, do you have any plausible explanations for this odd behaviour? Remember that people in question are "berter", so they don't usually act this strangely, they are usually the most predictable people in this world. A rather creepy conspiracy theory is that the "berter" are organizing, and becoming a more dangerous group than ever before... Oh well the experience is good for a laugh anyway...

Oh well, do you have any thoughts?