Its really secure unless you give out your private keys.
I like the idea of having a currency untraceable... you are the onlly one knowing how much you have and its completely safe with you
I think it is not that untraceable but it is psuedo anonymous. People will still be able to trace your transactions and balances but can't tell where you're from and who you are. But as you've said, bitcoin will be in danger if you gave out your private keys or maybe loose it.