Marketing tells a story that spreads.
Sales overcomes the natural resistance to say yes.
If you don't pay the salesforce (because you go direct, or you go free), then who is going to do that for you? The only answer that occurs to me is, "your users/fans/customers."
This means that a critical element of any strategy that ditches the salesforce is to figure out how you will empower and encourage your customers to take their place. Easier said than done.