In my opinion, the main risks are as follows:

1. Theft or loss by negligence
If an attacker gets access to the investor's private key, they can steal absolutely all the contents of the digital wallet.
2. Lack of security
One of the biggest risks is that the Bitcoin virtual currency is not backed by anything. Absolutely all national currencies of different countries of the world are provided with state assets. Electronic currencies are backed by the assets of the companies that created them.
3. Risks related to cyber-security
Hackers can hack into virtual currency trading platforms. For example, in August 2016, one of the largest cryptocurrency exchanges, Hong Kong's Bitfinex, was hacked and stolen 119,756 BTC, or $ 72 million, which led to an instant drop in the Bitcoin exchange rate by 23 percent.
4. Virtual Currency Fraud
Since the creation of Bitcoin, its adoption has grown exponentially, making it the most popular virtual currency used around the world. Unfortunately, with the growing popularity of cryptocurrencies, the number of scammers who want to make money on it also increases.
5. Lack of consumer protection
The unpleasant fact is that Bitcoin does not provide any consumer protection. The completed transactions can no longer be undone. All you can do after a failed transaction is trying to convince the recipient of the funds to voluntarily return them. This is a consequence of the fact that there is no intermediary guarantor, as in the case of bank cards.
6. High volatility
Fluctuations in the value of Bitcoin, in general, are almost unpredictable in the short term, and this adds to its riskiness. Financial experts can predict the value of the dollar, euro, and other real currencies or stock quotes relatively accurately.
7. The risks associated with the development of technology
The technological component often develops very quickly, and sometimes even uncontrollably. Everyone knows that Bitcoin already has and continues to have a huge number of competitors almost every day. Although Bitcoin is the most recognizable and popular cryptocurrency, there is still a very real technological risk that another more advanced virtual currency will appear. Investors simply may not notice the moment when their virtual funds lose their real value.
8. Regulation of the currency
Today, each country has its own approach to regulating cryptocurrencies. The lack of a single well-thought-out system for regulating cryptocurrencies only increases the uncertainty factor regarding their future. Regulators in many states are concerned that Bitcoin and other cryptocurrencies may be used for speculation, drug trafficking, money laundering, terrorist financing, and other illegal transactions. With the growing popularity of cryptocurrencies, the state authorities of many countries are beginning to actively come up with various legislative initiatives to regulate the turnover of Bitcoin and other virtual currencies.
9. Taxation of virtual currencies
This factor follows from the previous one. Investors who are going to invest in cryptocurrency should also take into account that there is considerable uncertainty regarding the taxation of the circulation of virtual currencies in different countries. In some jurisdictions, cryptocurrencies are considered an asset; in others, they are not.
10. The problem of network scalability
The problem of scaling the Bitcoin network has not yet been fully solved. Network bandwidth has long been a concern, and the growth of commissions makes small transactions not quite profitable (for example, transactions that are associated with the sale of BTC mined on Bitcoin cranes), and transactions with a large commission are also increasingly "stuck" in the network. Of course, they have been working on a solution to this problem for a long time, but so far none of the proposed options is an ideal solution. And if the problem of network congestion worsens, it will affect the position of Bitcoin as a payment instrument.