The problem with the NC is that it's counter-productive and does not achieve what artists want it to achieve.
It does nothing to stop people who do not care about licensing from "stealing" your work.
OTOH it stops people who feel strongly about licensing from using your work, making derivatives, making it popular.
It's terribly vague -- what does it even mean? If I use this CC By-NC picture in a presentation funded by a grant, is that "commercial"?
CC By-SA is way better.