Vitalik is not saying anything that we have not heard hundreds of times before and that any smart investor should know. Cryptocurrencies are a new and vulnerable technology and are very much speculative. Even in the best case scenario, many many crypto's will fail and fall to near zero. Worst case scenario they almost all will.

He is simply managing expectations and ensuring people do not enter the market with the wrong idea, we do not want these type of investors who think that failure or loss isn't a possibility.