It's good to scatter these unpredictably, because the point is that your opponents don't know where they are and die by setting them off (or else get discouraged from capturing territory when wounded; win/win). This makes Boobytrap another good candidate for automation (Alt+X), because it'll essentially just place them randomly, and has the advantage that it uses them immediately when the energy bar is full, so you'll get slightly more of them out overall.
I like to find corner cases, and try to make them interesting - this is Nethack's influence showing through. (Of course, Nethack takes it way too far; they made the interesting corner cases too powerful and broke the game, then tried to rebalance in light of them, thereby making them essential knowledge.) My original implementation of Boobytrap was a simple binary state, using the ability again on a boobytrapped vertex would have no effect. This wasn't really acceptable - not only is it less interesting than it could be, but if someone accidentally does it, their use of it would be wasted! So first I just made them stack, but it got a bit weirder after that.