Eric Ries is full of little gems:
They are exceptionally gifted salesmen. This is an incredible skill, one that most engineers overlook. True salesmen are artists, able to hone in on just those key words, phrases, features, and benefits that will convince another human being to give up their hard-earned money in exchange for even an early product. For a startup, having great sales DNA is a wonderful asset. But in this kind of situation, it can devour the company’s future.
The problem stems from selling each customer a custom one-time product. This is the magic of sales: by learning about each customer in-depth, they can convince each of them that this product would solve serious problems. [...]
This approach is fundamentally non-scalable. These founders have not managed, to borrow a phrase from Steve Blank, to create a scalable and repeatable sales process. Every sale requires handholding and personal attention from the founders themselves. This process cannot be delegated, because it’s impossible to explain to a normal person what’s involved in making the sale. The founders have a lethal combination of insight about what potential customers want and in-depth knowledge about what their current product can really deliver.