banok wrote: so when is someone aggroed? when anyskill is used/aimed at them?
As soon as they are targeted by an attack or move. For example, if I used Punch on you, you would be aggro'd and my character would start moving towards you. Even if the punch never connects (maybe you went through a door or maybe I walked off), you are still aggro'd by me.
banok wrote: too much mats, be cheaper just to let people take my stuff.
You say that now, but sooner or later "stuff you want to protect" will be worth more than "palisade materials." Even if your home is forever empty, your character's life might be valuable enough even now.
banok wrote: is a fence with no roundpole better since it make them commit vandalism rather than just trespassing?
Yes, assuming you mean no roundpole gate. Try this: Never make a roundpole gate. Leave a one-tile gap in the fence. Place your hearthfire there. Now you can walk freely, but an intruder must vandalize. This is still worthless compared to a palisade or brick, but it's better than having a gate and better than breaking the fence every time you want to exit.
It's probably a blessing that your sense of security (if you had one) was shattered.