No, not really. Open source embraces the idea of forking - a hostile take over of the original project is most definitely not the idea - but it can be allowed depending on the projects charter.
Also - most active contribute =/= maintainer - I'm sure Red Hat adds more code to the kernel than Linus these days, but Linus is still the 'decider'.
To conclude, Benno is free to fork GNU Nano, but it will not be GNU Nano - he can call it 'New Nano' if he likes.
Edit: That said, there seems to be more hostile takeovers happening these days. Perhaps because a new gen of devs care as much, or more, about brand as about code quality...
Changing name and leaving the old project eventually die or be subsumed by the fork (like egcs did with gcc) would have probably been a better choice.
I don't think Linus would object to someone replacing him if anyone was more qualified for the job. Hell he even openly encourages people to fork Linux, make improvements, and follow the license (copy left).
I see nothing wrong with the most active/best maintainer having say over the project's future.