You run the systemic risk of a trading platform failure
Whether it be accidental or intentional, if the platform (exchange) you trade on folds, you lose money regardless of the current price and the direction it is headed. This risk is negligible in case of regulated exchanges like CME, NYMEX and their likes, the ones that are trading derivatives. However, with cryptocurrencies, it is something that you should always be aware of, actually, be afraid of (apart from outright price manipulation by the platform of your choice). Put differently, your bitcoins are yours only if they are in your personal wallet (read, it is you who holds the keys from it)