Why sales, marketing, and PR all have to speak to each other

Tom Murphy points to the excellent post by Brian Solis, Why PR Doesn't Work and How to Fix It. My favorite part:

Figure out who your customers are and where they go for their information. This forces PR to mirror sales strategies in order to reach the people that could benefit from said product/service. Different people go to different places for information. First determine where you want to be and then work backwards from there.

I take a certain pride in my background as a sales representative. Most PR pros are trained in communications or have a background in journalism. Working in sales concentrates your mind as to why companies want PR, to increase their market share.