Haha. I agree with the rock horns thing. I do that quite a lot too. It becomes habit to do stuff like that, like whenever I am saying goodbye to my friend, we do this salute we got from the film "Moon Child" and I sometimes don't even realise I've done it until I see her doing it.
The question is, why do so many people do it? Is there a significance of the sign other than the usual "Peace" or "Victory" or is it just a cute thing to do, like another part of Kawaii culture?