In language of marketing, the "call to action" is what you want a customer to do at the end of delivering a message or conclusion of a sales presentation. Get online and order, pick up the phone, sign here...
In a world where markets are increasingly conversations (see book The Cluetrain Manifesto); and pull (being drawn toward something) is much more important than push (talking at or delivering messages to a customer or prospect), "call to action" is a weak idea.
A "call to adventure" is much more engaging.
A call to action is transactional; a call to adventure is an invitation to a journey, a relationship, and potential loyalty and advocacy for an offering or the organization that makes it.
Adapted from the heroic journey archetypes Joseph Campbell described in The Hero with a Thousand Faces and the analytical psychology of Carl Gustav Jung, a call to adventure is a more compelling idea for marketing professionals interested in sparking movements.
Movements are bigger ideas that campaigns - they are organizing principles that make categories more favorable organic revenue and profit growth.
Learning more about the dynamics and functions of movements are a call to adventure for the marketing profession itself.