Re: Why are soaps basic and shampoos acidic when they do the same thing?

Tough question and I am not a surfactant chemist (we don't currently have one volunteering through our site) but I am going to take a shot at an answer. First, here are some great sites that explain more about soap:

Surfactants Virtual Library
Chemistry of Cleaning
Bubbles, and there are more through the ChemE section of the MadSci library.

Back to your question - I believe the answer lies in the fact that the type of "soil" you are trying to clean is different, so the chemistry of the surfactant is different. Organic material is best removed with alkaline (basic) cleaners; inorganics are best cleaned with acidic materials... shampoos are probably trying to take care of both to get your hair really clean, so may be slightly acidic as a result.

I hope this brief explanation helps and I do recommend visiting the links I listed above for more details. ;)

Kieran