Complementary and alternative medicine, also known as CAM is becoming more and more popular--and not just for back pain but for many problems and conditions.
Right now conventional licensed providers include doctors, physical therapists, nurse practitioners, and physician assistants. CAM providers include chiropractors, naturopathic physicians, acupuncturists, and in some states, massage therapists.
There aren't a lot of studies yet to compare how much CAM is used. Many people have to pay out of pocket for these services because they aren't covered by insurance. This is slowly changing as states pass laws requiring health insurance companies to cover all licensed providers.