The main downside to bitcoin is all of the hacks and scamming. It gives bitcoin a bad name. But then again hacking/scamming is unavoidable as credit card details are often stolen as well. Security will always be an issue as long as people are greedy and feel the need to steal from others.
It's quite sad, seeing as the people with the technical know-how of how to hack these systems and remain anonymous would probably be able to start very profitable legitimate business that benefit the world.