Yes.  And Dan Cote says it is inevitable and essential in the social-network-oriented web world. 

I worked in an organization where documentation was part of the marketing department.  We were called Technical Publications and we wrote and published marketing slicks, data manuals, user guides, online help, interactive multimedia, even video as the liaison with the production house we used. 

I’ve worked in shops where technical communications was nested within IT or customer service or even project management, all of which are appropriate places.  However, putting a marketing focus on the materials we produced at the one place I worked drove us to produce more.  It varied our workload (which kept us from being too bored) and made us visible to the company and the customers.  Something that rarely happens with technical communication or training departments. 

Put another way:  when you think about it, we’ve always been co-marketers of the products and services we train and document.  It’s just that some of us have been  invisible.  But no longer.   

(h/t:  Ian Huckabee of WeejeeLearning)