Development of Creative Commons licenses

[P-M <cc AT phizz.demon.co.uk>]

On 19/12/2012 02:04, Ben Finney wrote:
> P-M <cc AT phizz.demon.co.uk> writes:
>
> > Walmart and Toyota know they are 'strictly from commercial' the local
> > band, and the community group know that they aren't, and should they
> > have any doubts they can fire off an email.
>
> So you're acknowledging that the license terms *don't* make clear who is
> allowed to do what. If the recipient is, for any reason, unable to
> contact the copyright holder, they can't know what grant of license they
> have.


If you want certainty and can't contact the copyright holder, how do you 
know that the BY-SA license isn't one of the flickr washed ones from 
wikipedia Commons?