There is a danger in conflating sales with marketing, or considering them the same function, when really they are distinct activities and requisite skill sets. But there is an equal danger in keeping the functions entirely separate, which is often where both programs (sales and marketing) come up short, with departments at large companies pointing figures and making excuses. There is both an art and science to achieving sales-and-marketing success, if only you can properly identify the obstacles and create manageable workarounds to address them.
Which brings us back to professional services firms