In my experience engineers are incapable of interaction with sales people. The difference in world view and personal experience is just too wide for the two to understand each other and effectively communicate. Just yesterday I've observed several instances where a sales person was using his charm and goal orientation to off-load to an engineer the work the sales person should be doing. And I've also observed several instances where engineers showed complete lack of understanding of sales people. While before we let engineers communicate directly with sales people, we now require all communication between engineering and sales be mediated by a product person who should act as an interface and an interpreter between the two worlds.
One big shortcoming of such approach is that the product person very soon becomes a bottleneck to information flow which slows down sales/customer support and product development alike. To reduce load on the product person and to alleviate the bottleneck you definitely need a sales/customer support engineer who can offload the product manager of operational duties and is equally capable of communicating with sales as with engineering, but most importantly, who can solve most of the issues him or herself without needing the help of an engineer or anybody else. This leaves product manager with enough time to collect feedback from the market and sales people and to relay it to engineers. And once market feedback is included in a new or update feature, product manager should spend enough time informing the sales, customers, and other stakeholders about the change implemented by engineers, a topic that I'll discuss in more depth tomorrow.
This is part of series of posts on managing sales.