But if you're following the advice in this article...nobody should ever know that you're not actually a real person. So you might "know" lots of folks online who are not who they say they are.
The identity and face of Daft Punk are very well known. Thomas Bangalter and Guillaume-Manuel de Homem-Christo have been djing without mask outside of that specific project.
that's just one theory. everything i've read lists both del naja and gunningham as possibilities at the least, and often tosses a couple of other names into the mix.
Law enforcement/intelligence services involvement raises the bar on maintaining anonymity a lot. They can access a lot of information that even an army of armchair sleuths probably can't.
Not "monetarily" as high value as some of the other examples here, but Icefrog, the lead developer/game balancer for Dota and Dota 2 is also mostly pseudonymous.
I think if it weren't for some stupid comments by a League developer (?), no normal people would know who he is. Now, if you try hard enough, you can find his identity leaked in an old blog/forum post (?) and have it proven/corroborated in other areas online I think.
Many others have tried and failed (though they often broke the law, so that might be the main distinguishing factor)