* During the sign up process, gender will be on the first page, and required.
* The only options are male and female.
* You will no longer be able to save edits your profile without specifying a gender if you have not set it.
Unfortunately, not everyone fits into a gender binary, and not every one wants to specify their gender to their journaling service.
So, why is this post going into no_lj_ads? Because this decision is nearly certain to have been driven by the need for better ad targeting. (Despite this, paid users must also give their gender. This is an example of how site development done to increase ad revenue can affect paid users, even though they do not see ads.) I don't know how things are for others, but I know that being in a female demographic increases my receiving of ads irrelevant to my interests or downright offputting.
Now, I feel I must note that this change has not come to pass yet. It has opportunity to change or be revised. Other and unspecified could be added, and the information no longer required. However, given the new aggressive interstitial ads, LiveJournal appears to be strongly seeking ways to increase its advertising revenue. Better targeting could help them do that. Given this, it might be possible that they do not change this, although you may not personally see why they would need this information.
If this upcoming development is not changed, and you do not want to give LiveJournal your gender or be forced to choose a gender that does not fit you, you should edit your profile before the next site update to something you are willing to keep for the remainder of your use of the service. I suggest putting your bio into a post and linking to it from the profile, so you can change it without running into the restriction.
ETA: Response suggesting this might not make it live, thankfully:
thank you for your feedback. This is all very informative, I received many email with this already.
However, the code update that you refer to is not live and did not have any chance to go live. That was a beta release, we always push code to beta to see if everything works correctly. In many cases it does not and we either fix bugs or pull the code from the final release plan.
We were going to add a gender field to the sign up user flow, which is fine, but by mistake it became a mandatory "female/male" field for everyone. This is why this is not going live. And this is what beta releases are for, to see problems and solve them before any user faces a problem.
I would appreciate if you share this information with your friends that are also concerned.
GM, LiveJournal US
However, the code to make the option mandatory on the profile was very much added on purpose (it's hard to write it on accident, so it's not a bug), so if there was a mistake in implemented, it was in miscommunication with programmers (or they'll decide not to do it after all). I'll be happy if it's true and she says this won't be going live--but I'm waiting until the next release at least before I'm entirely comfortable with the notion.
ETA2: We have rollback! And in unrelated news, apparently Nokia is going to be reskinning LiveJournal.