Trading crypto-currency, yes or noHanuman das
One devotee tried to make some money by inducing other devotees trade in crypto currency.
From Prabhupada’s books, we can learn that trading something which is intrinsically worthless constitutes gambling, and introducing others into the same nonsene additionally constitutes cheating. Prabhupada also called it speculation.
When we say that vaisiyas are engaged in trade, that means taking tangible goods from the location where there are in abundance, to the place where they are in scarcity. For example, taking butter from the villages and selling it in the city.
Also, trading crypto currency is zero sum game. That means only way for somebody to earn money is that somebody else has to lose the same amount.
Prabhupada tells a joke about kali-yuga vaisyas who speculate on the market.
“Prabhupāda: So this is government’s duty, that you are claiming that everyone should be employed, everyone should be engaged, in his own occupation. That is called svadharmeṇa idanasya(?). Sva-dharma means the brāhmaṇa, kṣatriya, vaiśya, śūdra. By quality. Guṇa-karma. By quality and work. So it is the duty of the government to see that a śūdra is employed, is engaged as a śūdra, a vaiśya is employed and engaged as… Just like vaiśya. Vaiśya, it is said that kṛṣi-go-rakṣya-vāṇijyaṁ vaiśya-karma svabhāva-jam [Bg. 18.44]. Now the vaiśyas, they are in the share market speculating.
Reporter: Hm. There are no more vaiśyas. (laughs) Exactly.” (Room Conversation with Reporter from Researchers Magazine,July 24, 1973, London)