I have noticed a bug in PVP. When I teleported to my friend watching a duel (in front of the fence) the creator of he duel somehow fled, and, to me and my friend's suprise, we could actually join the PVP duel.
It seems to be a very rare bug, but yes it does happen. It happened to me a one occasion, the day the level 48 spells were released to the public. I wonder if the bug's cause has something to do with high stress on the realms during busy hours? :?