I can cum while getting fucked. It's not a spontaneous no-touch orgasm. I have to jack it. But, yeah, I can get off while getting fucked. I think the key to it is - once again - strong kegel muscles. Ordinarily, the muscles that hold your ass closed, when relaxed enough to allow your ass to take a cock invasion, also let your hard-on go limp no matter how turned on you are. This is why most guys go limp while getting fucked. But if your kegels are in good shape, you can maintain an erection while riding the pony. And if you can keep it up, you're sure as hell going to be able to cum because, even if a half-decent fuck, you're going to be SO turned on.