YC partner Aaron Harris had a similar problem with his first startup[1], and is a lesson for all startups:
It's risky to rely on one customer for the majority of your revenue.
90% of PriceZombie's revenue was dependent on affiliate revenue, and thus Amazon. Similarly, virtually all of TutorSpree's revenue was dependent on SEO, and thus on Google, and when Google changed their algorithm, they saw a similar fate.
A similar thing happened to me with Google Images. They were unintentionally a major source of my traffic. Some years ago Google changed their Images service so that it continued to take images from other websites but was very unlikely to send people to the source.
It surprised me how little fightback there was to this change. So, anyway, never rely on platforms like that, always assume it's a temporary arrangement (especially if the platform is run by a major player).
It's risky to rely on one customer for the majority of your revenue.
90% of PriceZombie's revenue was dependent on affiliate revenue, and thus Amazon. Similarly, virtually all of TutorSpree's revenue was dependent on SEO, and thus on Google, and when Google changed their algorithm, they saw a similar fate.
[1] http://www.aaronkharris.com/when-seo-fails-single-channel-de...