Answer :
They are often prosecuted if someone decides to report this. Tell me, what is the difference between stealing virtual object (which is worth certain amount of money) and stealing a mobile phone? I do not see any. Every object, even in game, is worth some money. Therefore, taking it is stealing.
A person would be prosecuted if he causes threat, or loss to a persons emotionally or physically. Since virtual objects dont have emotions they are not harassed by any means.