The ability to make something go viral is both an art and a science. On the one hand, the art of going viral is synonymous with luck. While on the other hand, the science of going viral is typically attributed to skill.
When you are bootstrapping your business, you just don’t have the luxury to spend money on advertising that requires luck for success. This is why the vast majority of bootstrapping entrepreneurs default to word-of-mouth advertising as their only strategy to grow virally.