Main fear is lost investments for some reasons like red market,when long time all prices drop,some new restrictions on cryptocurrencies that do not make it possible to freely dispose of, make transfers, etc.
Also, now government bodies are actively taking control over these assets in order to tax these operations, even many cryptocurrency exchanges already cooperate with them and have KYC on many, which makes it very easy to track who, how much and where transfers and withdraws. So surveillance is one of the main enemies of cryptomaniacs for making money.