Umm... If that's how it worked we'd call it LZ (or whatever variant thereof) compression, right? Someone knew the format before Nemesis. If you don't want someone else's name written on your guide, you don't make a wiki. If you don't mind, then you do.
It's different if someone decides for you. If someone puts his name on your work, then it's not your choice, is it? =P
e.g. If I suddenly pick up my copy of Nemesis' hacking guides and put my name on it, it doesn't make them mine, but he's likely not going to do anything about it, because he's not around. That doesn't make them mine, and it doesn't make it right. Yeah. That's it.
All changes ever made to a Wiki page are preserved in the page history. If you want to see what a user wrote about something, open up the history and look for that user's name. On the same coin, if a user wants to prove that he wrote something, s/he can find that edit and link to it. In short, nobody can put his name on your work when it's in a Wiki. They are allowed (and encouraged) to modify it if they have new or better information, but diffs (with associated names) are preserved for every edit made to that page.
And hey, if I want my name on something so badly, I can change it whenever the heck I want to have my name there. -Written by LOSTGAME!!! GIVE HIM CREDIT FOR THIS POST!!1!!1!!11!