How to sell - and buy - ideas The Idea

Why don't digital and advertising agencies sell their products like other businesses?  Is selling beneath them?  Or are they so close to their clients that they just don't need to bother.
Nick is joined by leaders from client-side and agency-side to explore how ideas are sold and bought.  
And as project-based arrangements supplant traditional AOR relationships, Nick suggests that now is a good time for agencies to sharpen up their sales skills.