We've already seen 3D print services try to overcome the "I don't know how to build a 3D model" problem by specializing in pre-made designs. Typically minor customization is offered, such as color, size or adornments. These services have been very successful, as the majority of the population doesn't have a hot clue how to generate printable .STL models.
Another example of this approach is JuJups, the Singapore-based 3D print service, who have recently announced the ability to print 3D Angels, Santas and Elves. They're trying to not only specialize and simplify for customers, but also focus on a seasonal product. The service is unique as you can not only choose hair and accessories, but also you can upload a photo to be placed on the face.