You should absolutely be very careful about working for an early-stage startup as an employee and taking options or equity in lieu of part of your salary. You should feel that you trust the founders. You should insist that they've figured out a.) who their customers are b.) why they want the product and c.) how to make money, and have some concrete evidence that the customers do in fact want the product. You should ask about the cap table, and liquidation preferences, and anticipated future dilution, and know what percentage of the company you'll own and how much you'll make under a variety of exit scenarios.
But if the numbers look good and you have solid evidence that people want the company's product, oftentimes taking more equity is the right move. Equity aligns your incentives with the company and ensures that if it does well, you do well. Under capitalism, taking cash is a loser's bargain, not in the sense that you always make less money (you often make more), but in the sense that cash dominates equity only if you've picked a losing organization. To the extent that most organizations lose, this can be rational, but to the extent that you're an independent economic actor trying to maximize your returns, it's often worth putting in the research to try and maximize your chance of picking a winner, particularly given the other career benefits of having a hot startup on your resume.