Not necessarily. If your solution is solving a real pain point or is creating something really valuable for your potential customers, you can ask them to pay upfront even before the MVP is ready. Treat them as your extended team taking their inputs while you build the product. Easier said than done but its the best validation you can get. You may have to grandfather them on pricing though.

Have a look at this mixergy interview for some ideas/inspiration - http://mixergy.com/sam-ovens-snapinspect-interview/