I’ve wrestled with this as well – http://blogs.educationau.edu.au/kjohnson/2008/02/28/obligations-to-the-subjects-of-creative-commons-licensed-work/
and really feel that cc:by isn’t enough. My main concern isn’t the use of MY stuff in a commercial way but the use of the SUBJECTS of my photos having their images used in ways with which they would not be comfortable. By putting in NC I am not shutting the doors to my photos being used in a commercial way — it just means the interested party has to negotiate with me first.

I understand where Stephen is coming from with the SA addition to his licensing — but there are too many educators who would not be able to comply because they don’t own the copyright to work they produce. The government or institution for whom they work owns the copyright to work created during work hours using work equipment for use at or for work. And governments traditionally want copyright ownership. Full copyright ownership.