penetration is an (almost) absolute necessity for me to orgasm; i orgasm (almost) every time I have PIV sex. after years of perfecting this method, i've decided it's both a combo of the penetration (and stimulation of my gspot), and the indirect stimulation of my clit from my partner's pubic bone. in order to get off from rear-entry positions, my clit either needs to be pressed against a pillow/blanket, or i need to be lightly touching it (just holding my index finger next to my clit works for me perfectly). but i also understand i am in the minority in this camp.