LJ wants you to identify your gender.
abbylee has a wonderfully detailed explanation
here. I give you three guesses why, one for each letter in the answer, which begins with an A and has a D in the middle and ends with an S. So there are two levels of ick here: one based on making people identify their gender on LJ, which is problematic for a giant number of reasons (starting with the fact that some people don't identify easily with one gender or the other and shifting on over into privacy concerns for those who do), and the other based on the fact that this is clearly a move to target ads better. It's important to understand that that's a crucial part of the current LJ business model.
Walked back. At least for now.