Fraud (phishing) has been known in the online world. Phishing occurs when fraudsters create emails, messages, login pages, and / or websites that look like authorized and trusted companies. When users enter their information (such as username and password) on the fake website, the fraudsters will have access to the user's account. If the account is an account where Bitcoin is stored, then the fraudsters will easily steal your Bitcoin.
If a user has the same password on multiple sites, then fraudsters may access other sites containing more sensitive information.
It is right that care is important in bitcoin business and I think everyone is so careful in this case. Bitcoin is secure because block chain is not so much weak system that it may be hacked. Wallets are secure, due decentralization government access to bitcoin accounts are secure, and we can openly trade, so I think we dont need any fear to have business in bitcoin.