Travel insurance is worth purchasing for big-ticket trips that are largely non-refundable. The typical plan will cover emergency medical expenses and baggage loss and delay, and recover at least some of the cost of your trip if your vacation has to be canceled or cut short (the amount is partially determined by which state you live in), including if the travel operator goes belly up. Note: Most insurers consider a layoff to be a valid reason to cancel a trip.
Always buy from a third-party insurer, not the company selling your cruise or tour. And considering the fragile state of the insurance industry these days, you'd be wise to choose a large, established company that's less likely to go under, such as American Express, instead of one you've never heard of. Other reputable travel insurers include Travel Guard, Medex and Travelex.