There are a few disadvantages of Bitcoin. The most discussed one is the speed of transaction which is really bad when a lot of people decide to move their BTC somewhere else. However, SegWit has been already activated and we have to wait for its implementation on big services. As far as I know, there was a successful Lightning Network test on Bitcoin testnet. It should help us to solve this problem. Bitcoin in not as anonymous as many people think. Some government authorities have already developed tools which help with tracking spent coins. There is a proposal of introducing Confidential Transactions.