You need to know bitcoin wallets and security. This is possible problems that malicious software can scan your disk and find your private keys. Seconds later, all your Bitcoins can be gone. A trojan can encrypt all the files on your hard drive. Afterwards, it might find all links to your wallets, realize how much money you own and demand that exact amount of Bitcoins to decrypt your hard drive. A virtual exchange can run away with your money. You can lose your laptop or your phone with your wallets installed on them.