When I find a new cool library or program on github I often have trouble finding the "official" or "best" version. Many times it is of course the root repository of all forks, but often the original developer moved on and someone else picked up his work. If there are only 2 or 3 forks I can check them all, but more is impractical.
When I put stuff on github myself I often lose interest in the software, but someone was nice enough to fork the project and keep working on it. Unfortunately my project will still always be displayed as the most important version.
Some software developers have decided to create a shared account (or, since Github now supports this too, an "Organization") to prevent this problem (see for example github.com/ruby/). When one developer decides to leave the Ruby developement team, he is simply removed from the shared account/organization, but the project URL stays the same.