The biggest disadvantages of Bitcoin is that people do not use it widely. I live in a country where only a few people realize the benefits of bitcoin. Thus, there is no store, no shop, no ATM accept Bitcoin. Furthermore, Bitcoin does not have CEO or any company, so there is no advertising campaign which can make a significant effect to people's knowledge about Bitcoin and change people's thought about it
Right also in our country some thinks it is used for illegal transactions and for bad things. Though now some were open and becomes curious knowing bitcoin. I just hope it can expand more and be accepted by everyone because it can reall help the rich and the poor , they must know how good the bitcoin is.