I've done this before in a group reading (about 5 of us sitting at a booth at the local Waffle House trying to determine the meaning of the spread). Everyone was getting overtly frustrated since we obviously all had different opinions and interpretations of the cards. So we would each interpret the card and use the pendulum to determine whether or not the interpretation was accurate for the current situation.
I had a lot of fun, since it turned out no one was right at all until we discovered where we were going wrong by throwing out a lot of yes/no questions about the cards. Eventually, we discovered our answer, and were all quite satisfied with the results.
Of course, the others wanted to strangle me with the pendulum chain, but that's because their egos got in the way and were upset that they were overlooking what the cards were saying. That's just my experience, though. I haven't really ever read into the topic. I had originally just been playing with the pendulum (I get bored easy and when I'm bored, I get compulsive) and suddenly they asked something and it responded strongly, so thus began that little adventure.