I did some market research to see how 3D printing could be applied to shoe design.
An amazing designer named Earl Stewart highlights some amazing things you could do with a 3D printer. http://cargocollective.com/earlstewart/XYZ-SHOE
Even Nike has ventured into the 3D printing market, by printing the sole for their cleats.
New Balance has allowed their customers to custom make the sole of their shoes to fit their preference.
3D printing has even crossed over to fashion, and some high end fashion designers too.