There are so many small magnets around that are very strong a compass can easily be ruined if you get it too close to one.

The magnets I am talking about are those small rare earth type magnets which are now used for tool attachment, door closers, fridge magnets, and all sorts of other innocent looking devices.

The older magnets were usually weak enough not to be a threat to your compass but the new rare earth type magnets are strong enough to permanently change the magnetic alignment a compass needle if they are near the compass case.
So be careful around them and try not to put you compass into the same pack with one of them.

I currently have three button compasses that point southish instead of northish.