You can get revenue from many sources, as in many individual customers, but be dependent upon a single source for your product. The situation of startups who d

You can get revenue from many sources, as in many individual customers, but be dependent upon a single source for your product. The situation of startups who depend upon an external large business like Facebook, Amazon or Twitter is analogous to a car dealership that only sells one kind of car - say, Saturns. If Saturn stops selling to you or goes out of business, you're going to have to make some major changes.