Experiment
Given that it must be common knowledge to anyone with half a brain that all nubile young girls in cybersex chatrooms are in fact men or boys of varying ages, a scientific test was needed to measure exactly how much people cared.

Process
Logged on to an IRC server and joined a few cybersex channels using the nickname PretendingToBeAGirl.

Outcome
At first there was silence. Then a bleep. A private message, contravening the channel rules about asking before messaging but, hey, I didn't really care...

(namewithheld) so ur a guy?
(PretendingToBeAGirl) yep. hello. wanna cyber? ;)
(namewithheld) sure, okay.

I. Kid. You. Not. I pretended to be a busty female future-cop in an all-over rubber uniform (his idea) and he was a criminal that I was to - ahem - interrogate. I haven't laughed so damn much in ages.

I got a few other messages as well. Some just curious about my nick and some didn't mind a bit of cybersex. Sure, it got boring after a while but, still, it was hilarious while it lasted.

Conclusion
In conclusion, it is common knowledge to anyone with half a brain that all nubile young girls in cybersex chat rooms are in fact men or boys of varying ages and, to be honest, there are people that really don't care, so long as you're willing to be what they want you to be. And, to be honest, why should people care? It's not as if any long-lasting relationships have emerged from online cybersex. Most people are blissfully aware that the woman on the end of a sex phone-line looks nothing like the woman on the sex phone-line advert but still, somehow, people get off to them. Just as long as people get what they want, I don't see any harm in that.

update: i have also tried the same 'experiment' with the nickname PretendingToBeABoy and considerably more successful results. boys would message me and think it 'kinda cute' when i told them of my plan and then they'd pretend to be a girl.