Bitcoin is a non-guaranteed money unit
Bitcoin trading is only one way, which means that when you transfer money to someone, you can not withdraw your trading order. Therefore, if a hacker grasped your "bitcoin" tag, he would have total control over how much money you had and then, inevitably, loss.
Bitcoin trading is based on a one-way mechanism
However, if you use third-party virtual money storage services to protect your money from hackers, you can still recover some (or all) of your lost money. Typically the Instawallet virtual wallet store has been shut down due to hacker attacks and its owner has compensated the attendees.