Could you elaborate on whether inflationary and deflationary cryptocurrencies are inherently problematic? The question arises due to the varying economic impacts these monetary policies have on a digital currency's value and stability. On one hand, inflationary currencies tend to increase the supply over time, potentially leading to devaluation. On the other hand, deflationary currencies, with their limited supply, might lead to appreciation but also hinder widespread adoption due to high entry costs. Is there a middle ground or a preferable policy for cryptocurrencies to ensure their long-term sustainability and growth?