We all love the certainty of the solid revenue that comes from a big customer. It gives us credibility with other prospects. It pays a lot of salaries. Occasionally we reflect on the risk to our business if they left us...most of the time we don't.
Yet the tyranny of the major customer can help us hide from the real foundations of creating a repeatable sales process or building products that many customers want. It can keep us too focused on the needs of that major customer.