It is extremely easy to dupe all items. If you get fully geared and meet up with a friend all you have to do is simple.

Knock the person with the gear unconcious but do not kill them, proceed to loot their body but do not take anything.
Get the unconcious player to log out before you have taken the gear.
Once they have logged out completely, take all their gear before they relog.

Upon relogging the player still has all of their gear and you also have their gear.