At first glance, the meteoric rise of blockchain mining specialist Marathon Digital (MARA) provides an inspiring backdrop for speculators. Knowing that cryptocurrencies can spark dramatic valuation spikes at a moment’s notice, Marathon seems like an attractive buy. However, this unpredictable nature also makes it inappropriate for arguably most investors. I am bearish on MARA stock. As a mining enterprise, Marathon Digital is tied to the ebb and flow of bitcoin (BTC-USD) prices, which simultaneously represents both the opportunity and the pitfall of MARA stock. On the one hand, when cryptos soar, there are very few markets that deliver a similar magnitude of profitability over a relatively short period of time.