I started my MU* career back in those days of yore. I took about a 10 year hiatus, and when I came back the OOC Masq was a thing of the past, character wikis were now a thing and people were free with everything.
At first I hated that it no longer existed. I thought that it spoiled the game, that any element of surprise was taken away. That no longer would someone be in a bar and pick a fight with the wrong person since they could just look up what that person was and go 'Oh, shit..he is a insert thing here and I am just a lowly mortal. Maybe I should edge back so I don't end up dead!'.
But, after a bit I noticed that people (at least most people) didn't use the OOC knowledge they had and actually played their characters ICly, and that the prospect of being open actually enhanced some of the RP because you could add some prose to a pose that you otherwise wouldn't have been able to because of the OOC masq.
That being said, I wouldn't mind seeing an 'Old School' game with the OOC Masq pop up, just because I did like the element of mystery that went along with it, but I also know that I am in the minority and people tend to find the OOC Masq a horrific thing.