The Startup Sales Challenge

It's long been said that the founders of a startup should remain directly involved in sales as long as they can. Does this help or hold back the progress of the start up? An argument can be made either way.

What better way to stay in touch with customers, monitor how they receive products and ideas? Who has more passion about the idea than the founders who are personally committed to them from the beginning? Clearly the Founders should stay directly involved in sales and customer engagement, but as the task takes over more and more of their time, when and how do they move from being the only sales people to beginning to grow a sales team.