In How Soon Do You Need a Product Manager, I argued that product management should be hired very early in a company's life. In The Influence of Tribes on Product Success, I told of what happened to one start-up that did not successfully managed the gap between technology and customers.
It turns out, I'm not the only one who feels this way. Check out this post by Saeed at On Product Management blog. In short, Bill Campbell, CEO of Intuit agrees.
If you have a start-up, don't under-estimate the value of a product manager. It is about far more than just prioritizing features!