I came across this post by a professional writer which I wholeheartedly agree with, so I decided to link it here:
http://laurierking.com/wp.php/?p=463 The points she makes are excellent, and it's something I've thought for years. That is why I will always try to buy new rather than getting stuff second hand if I can possibly do so. If I buy new then I have the satisfaction of knowing that my sale is being recorded and the reward is going to the person responsible for doing all the work and publishers know that there is still a demand for the things.
It also works to a lesser degree with fanfic. If you like a writer, then comment on their stories. If you don't, you may disillusion them into thinking they are no good or giving up their writing. After all the only payment a fanfic writer is asking for is feedback, they aren't making any money out of it, like the professionals do.