IRC and anonymous or pseudonimous fora are still out there, and there is no trend in forcing gender choice in them.
Those of us who have been here for long enough to play with online personas and to enjoy intelligent use of anonymity are bound to feel nostalgic, but I honestly don't see a trend so much as I see the real world's biases finally catching up with the internet, where's the space for everyone and then some.
Of course -- however, the default used to be "On the internet, nobody know's you're a dog." There were very few sites, especially online communities, that would require your real name; of those that did, very few of them would require its disclosure to, say, search engine crawlers.
Those of us who have been here for long enough to play with online personas and to enjoy intelligent use of anonymity are bound to feel nostalgic, but I honestly don't see a trend so much as I see the real world's biases finally catching up with the internet, where's the space for everyone and then some.