My biggest concern regarding Cryptocurrencies would have to be these scammers and hackers because you really can't tell when they'll hit you as their target. And with the internet that's so open, even if you have the safest wallet there are still times they could hack your account information and get your money out of nowhere. Some are even taking advantage of the untraceable blockchain technology we have and steal from people which are one of its disadvantages.
Scamming is widely happen on the ICO investments buddy. So if we are good at checking the perfect ICO you will not be get scammed by anyone. Hacking is the worst thing happening in the bitcoin and other cryptos. Recently some trading site, nice hash server and indidual hack on the online wallets increased more.
Due to this people whoever wanna invest on the crpto currency will be fear about that. Hopefully encryption level may increase and it would avoid hackers to target the online wallets and trading sites.