Sulfates remove a lot of oil from the scalp -- which isn’t meant to be completely stripped of grease in the first place -- and consequently, your skin freaks out and goes into oil-production overdrive, which Dr. Kogan describes as starting a "vicious cycle" of hair treatment.
Oh yeah, there's one more problem. As Pazos notes, "[Sodium lauryl sulfate] has been discovered to damage DNA," and you kind of need your DNA.
"In most European countries, it’s illegal to use paraben and sulfate shampoos," adds Napoleon. You Europeans with your universal healthcare, excellent mass-transit systems, and superior chocolate... now you've got to rub your shiny, carcinogen-free hair in our faces, too?