I think there's one major reason for not C&Cing that seemed to be missed
in the (otherwise excellent) article. Or at least, it's the reason I
don't C&C as often as I'd like, or should.
I'd rather be writing.
C&C draws from the same pool of time and enthusiasm that writing does,
and the vast majority of the time it's easier for me to spend both on
churning out the next chapters of my own work.
I now try to send at least one line "liked it" comments to the authors
of anything I enjoy, but sometimes I forget, and to be honest I don't
read nearly as much fanfiction as I used to. I'll flag an interesting
story to read, but it'll slowly get buried in my inbox, never to be seen
again.
I certainly mean to (once I catch my breath from the start of a new
semester at school) redouble my efforts to C&C, but I have little doubt
that this will have no more effect than my previous attempts to do so.