Is taking a shower unnecessary if good bacteria surround our skin?
the Phrase "good bacteria" doesn't mean it's not gonna be harmful to you . actually they called : normal flora . they are refer not just to bacteria they include all types of microorganisms . 
http://www.ncbi.nlm.nih.gov/books/NBK7617/
I give you an example : there is some bacteria in our bowel they help our digestive system to work better . but these bacteria in case of some infectious disease or in the people with Immunodeficiency disease like AIDS turn to be pathogens .
the vision of David Whitlock is not irrelevant in fact in the field of industrial biotechnology we use micro organism to clean and digest environmental pollution like oil spills &amp; ... just like him use bacteria too clean out his body but in fact the thing is he put non pathogens bacteria on his skin so there is no place for other bacteria . 
but as a professional view  there amount of normal flora on our skin is 10 times more than our cells so you can not think our skin is a surface and you can just wipe every thing on it just by showering and ... I'm telling you these thing are odd and there is no scientific evidence that support this odd things . maybe in 100 years when we ran out of drinking water we force to make cleaning sprays base on this view . but you know such a crazy but possible thing in theory .