Women were comparably more fond of ICQ and even now it's them who still hold on to it. It's very unlike the IRC sausage party. I think you would more likely to run into a girl pretending to be male.
Also, I have this feeling that it's much harder to disguise your gender in Russian than it is in English. First of all, everybody has it as first language with all its nuance and can guess a lot of things about their penpal. Discussions are also deeper, making it harder to fake.
Anyway, it was more about talking than about romantic relationship. Not many people expected to ever meet their virtual friends.
You can definitely ruin that, for example, if you do not randomize well enough and a small subset of user base gets too much attention.