Giant ponzis do not run for more than 10 years. At $600,000,000,000 invested in Bitcoin the money supply has dried up. Bitcoin has crashed from $20,000 to $12,000
and high profile people calling Bitcoin a giant scam there is ever increasing risk of international police raiding Bitcoin mines
There are countries where bitcoins is being used as a pyramid scam and ponzi, that is the reason why there are people who cannot fully trust cryptocurrency as a good asset to invest but if government will be legalizing cryptocurrency then most of the people will still believe on its growth and the demand will keep on increasing in the market.