Places a 'hello my name is' field at the top of the page. Any name typed into the field is assumed to be the right proper name of the user, no checks, no questions. Just like a name tag.
Obviously this is not acceptable to all people, nor is this for all sites. However, if you want to build other authentication mechanisms, like for saay, SXIP, openID, or whatnot, you could probably put some in-between logic in there. The point is that trac doesn't care anymore who you say you are, it just believes you.
If you have any issues, create a new ticket.
Download the zipped source from here.
There is a box that says "Hello my name is Hector Petelbaum" change the name, and you've changed your login, it's that simple.