All Bitcoin transactions are public but it is not always known the real identity behind any give Bitcoin address. Scammers target new Bitcoiners and less tech-savvy users. Bitcoin is also very unique compared to other markets in that it trades 24 hours a day and never stops. Certain exchanges are simply there to steal your personal information or rob you of your bitcoins. Their value is completely derived by market forces of supply and demand, and they are more volatile than traditional fiat currencies.