I have several times mentioned the Gentoo Wiki as a great source of information for users of other distributions. It used to be a great handbook whenever I wanted to tweak some lightweight window manager or was trying to do some other obscure things with my desktop.
Unfortunately, the administrator of the Wiki did not consider the information valuable enough to be backed up:
Gentoo-Wiki recently had it's database lost; this is the rewrite of the site. Please visit the Main Page to see how you can help.
For me, the Gentoo Wiki was the only reason why I even considered installing and using Gentoo. For some months, I actually used Gentoo as my main desktop. The fate of this wiki makes me wonder, if I should ever participate in collaborative writing efforts if the platform is not collectively and reliably backed up. I don't care if you lose all of your own data, but losing collectively written documentation means the administrator and the project did not value the documentation at all.