This does happen, I've had members of our BH and friends from other BH's that put auto crew hiders on when they went to bed, they get up, secure the few that are out after the crew hiders run out. Securing twice to make sure everything got sent. They went to fix a cup of tea, for about 5 minutes, came back to find that their entire fleet, dreads, ships pirates, everything had been taken out, and then all of a sudden a certain member that had a vindictive steak against a member had attacked and took everything out. Now tell me, how does a person secure their troops, everything else was in the harbor,leave for 5 minutes and their entire fleet just suddenly comes out of the harbor while he was away for 5 minutes? This is either a bug or purposely done by plarium. I've had many friends leave the game because this is happening over and over. Fleet doesn't mysteriously just pop out of the harbor. You either have to take it out, or it's taken out from the inside, like developers or programmers that does this. Why would someone do this? and then out of the blue someone that had an issue with you from long ago comes in and attacks. Coincidence? I don't think so.
They are losing long time players with this type of actions. People who had spent tons of money in the game, and the time spent building up their havens and fleet, to have something like this done to them. But I can say if it ever happens to me, I'll quit also because to me, this is cheating on a major level.