Well, I try to keep my online persona in the asexual camp, hence the largely genderless/ambiguous handle (chosen as such). I'm never entirely sure exactly how it's come across, or whether there's certain little tells. I HAVE had people guess me both as - or more accurately assume I was - female and male on previous occasions. Mostly I don't worry about it that much, it's just something to occasionally ponder. When we're interacting mostly on an intellectual, plaintext level like this (or IRC etc) I can't see how it matters, right up until the point where exclusively guy- or lady-things are the subject matter under consideration, or a POV from one or the other is required.
I've come across things like eunuch dot org before and found them fascinating, in much the same way as people who choose to have various limbs amputated or do other major body mods. For some it's a serious case of gender or other body dysphoria, others a morbid bit of experimentation. A small few it is genuinely a desire to be asexual and of course sterile, and without the usual hormonal drives. It strikes me as a bit odd. Such things can be achieved chemically and reversibly if you really want to give it a go, but unless you're suffering the whole "X in a Y body" problem, these drives are a serious and natural part of your mental as well as physical makeup.
(oh, and it does largely but not exclusively seem to be men, which one can only assume is because the relevant parts are so much more easily and safely removed. The female equivalents largely boil down to removing or modifying the obvious external parts (and of those, the downstairs more so than upstairs), leaving the actual crucial bits unscathed because they're so much harder to get to, making the surgery far more risky too... despite the ultimate effects being arguably far more beneficial for the individual in question. No periods, no uterine/ovarian/cervical cancer, less chance of osteoporosis, etcetera - versus a slight reduction in agression, slightly improved clarity of thought and vaguely longer life (and eradicated risk of testicular/reduced risk of prostate cancer) on the other side)
Now, what would be fun - or at least deeply intriguing, for obvious reasons - would be the ability to be bi-sexual in the true sense, or even more so flexi-sexual. Medical and general science, not to mention the whole ethical structure, would have to undergo a massive step change before we could even consider such things, but it's fun to dream. And it brings a huge amount of erotic amateur and fanfiction to life
I could see it happening eventually though. Enough other surgical techniques originally designed and used for the benefit of those suffering genuine disfigurement or injury have eventually been hijacked for pure cosmetic or elective use. A combination of stem cells, tissue printing/frameworking and nanomachinery, initially used to allow or aid recovery from horrific injuries and diseases gets seized upon by female-male transsexuals for its ability to solve ... ahem ... what you may call a long-(not-)standing problem in the whole process, diversifies into giving both sides of the trans coin long-dreamed-for full fertility in their target gender, and before long the wealthy (or intensely curious and willing to save up) "cis" community are having cosmetic mods on the same lines, possibly with the ability to switch back and forth at will, with a few weeks gestation whilst the nanos work their magic. (I'm no fool, I've read the "Virtual Hell" edition of Adam Warren's Dirty Pair adaption, I know trying to have it happen in less than about a day would result in you catching on fire) ... just one more variation of all the other cosmetic enhancements you'd then have available due to said technological and ethical revolution, up to and including full limb replacement and all-over body rejuvenation. Brave new world.
Mostly the ability to have a date with someone as one heteronormative gender pair and then do the next with you both the opposite would bring an interesting dynamic to it all and also a fair old bit of equality. Or you could just freak them by swapping unannounced in between two meetings and see how they cope
