there are no 'public servers'. The 'servers' are hosted by players, same as your adventure with your friends, and whether or not you get punked depends on who you are playing with. There are the ward and personal chest and such to protect you, somewhat; I don't know how effective they are against a determined pest. Supposedly there are servers with death traps at the spawn in point, trapped in a cycle portal gates, and other foolishness on top of people wrecking your stuff from time to time. And there are also apparently many servers where people have a great time together. Find some good people, and enjoy the ride.