Of all the chemical families, I think of sulfate salts as among the most innocuous. Yet, especially in a Whole Foods or similar store, most of the shampoos boast of sulfate free formulae. What am I missing? What’s the advantage?
Some people are allergic to the sulfates in shampoo, if I use a regular shampoo my scalp will be painfully itchy, and I have scratched so bad I’ve made my scalp bleed.
Also the sulfate salts strip colour more than sulfate free shampoos.
Googling around seems to suggest that it’s usually touted as gentler on colors, though I didn’t find anything that really substantiates that.
It reminds me of this comic though
http://www.xkcd.com/641/
From what I’ve read, sodium lauryl sulfate can cause allergic reactions or irritation, while sodium laureth sulfate is mild and gentle. Since they’re often used together and are easy to confuse as well, I suspect they get tarred with the same brush.
There’s also a very popular book out now called Curly Girl, which is an owner’s manual for curly and wavy hair, aimed at people who hatehatehate their frizz, or (like me) grew up with straight hair and discovered it’s actually wavy/curly.
In it, the author writes:
pp 11-12
She goes on to claim that frizz is due to the harsh action of vigorous lathering and sulfates on the cuticle and the drying effect, causing the cuticle to open wide “to reach out for moisture from the atmosphere, hence the frizz.”
Now…there’s a whole lot of non-citing going on there, and I don’t want you to ask me for cites, because they’re not my claims 
but the argument is common and popular right now. As I’m doing research to figure out WTF to do with my suddenly curly hair, I see the same argument on nearly every webpage devoted to curly hair care. As long as people believe it, manufacturers will exploit that belief and sell them what they want - sulfate free shampoos.
That was the one thing I had heard, and since it was irrelevant to me, I didn’t pursue that area.
Like the comic!