Does your product solve a problem?  Or does it fulfill a desire?  This is an important distinction.

If you are solving a problem, your marketing challenge is all about getting the word out to your customers.  If you're selling a cure for their sickness, they need to know where to go and who to see to cure their disease.

But if you are fulfilling a desire, your marketing challenge is not about simply communicating with a large number of people.  To market a product that fulfills a desire, you need to paint a vivid picture for your customer – the customer needs to see and feel in their mind how your product fulfills their ambitions.  That's a different task.

In all likelihood, however, your business will need to solve problems and fulfill desires, at different times and for different customers.  

The most important marketing challenge is to know which situations call for which approach.