The good news is that there are a couple new firms that aim to address this exact issue. The firm I work for is called the Employee Stock Option Fund (ESOFund) and we aim to help employees exercise and cover the taxes associated with the exercise (on a non-recourse basis - meaning you don't have to pay us back if the company fails). In exchange, we split the future profits. If you use us, it is a risk-free way to exercise with a chance of significant profit in the future!