from the LA Times:

To Jannini, it’s clear: Some women have extra-thick, sensitive, different tissue in the front wall of the vagina, whose stimulation can lead to vaginal orgasms. Other women don’t. (Call it a G spot if you like, he says; until there’s a formal definition, the label is more about marketing than science.) Thick or thin, though, it’s all part of natural variability, Jannini believes. “A woman without the so-called G spot is perfectly normal,” he says.

alternate titles for this post:

Going, Going, Gone: The New G spot
Getting over or Getting Off: G spot Inquiries
G spot Haves and Have Nots