Usage of your Art: Is not being paid for it okay?

For me it has been free use of my work in book compilations/collections, where I have been paid is for cover work from publishing companies. Usage of your work in artist collection books is a great way to promote your work with the cost only being your time and cost of producing the photo. Marketing yourself in a photo or illustration book can start from $1800 and up, those books are sent out for free to agencies, but I have found that the usage of them has gone down dramatically because of the internet. I believe that usage of your work in book collections and group shows are great free marketing...but commercial usage should be paid for. 
From TechCrunch:Is Uncompensated Commercial Use Of An Artist's Content Really That Bad? We've discussed a few times how the whole distinction between "commercial use" and "non-commercial use" can be somewhat arbitrary. Even though many Creative Commons supporters insist that a "non-commercial" license is the way to go, there are some good arguments as to why such a limitation isn't a good idea either. MORE>

Nina Paley