Development of Creative Commons licenses

[Gottfried Hofmann <toddd AT mypse.goracer.de>]

> IMHO quite the opposite: every dedication to the Public Domain 
> undermines the Open Content movement. PD work can be used without giving 
> anything back. It will not grow the commons. I can easily see companies 
> pushing PD and PD-alike licenses to allow them to take people's work: 
> see the sudden liking that Microsoft/AdTI found for the BSD license when 
> faced with the success of the GPL.

If CC is about giving back, then why is SA optional?