I tried Niamak, but soome silly man touched the flag before i had even set the first trap, and even though I mentioned that I would be trapping to the whole group many times, there were still a couple who just ran around everywhere like they need to touch every hex on the map at least once >.<
Still waiting for a good opportunity, but I have attempted a successful pvp ambush using traps by myself, however. So I can attest to their effectiveness in certain situations.