Some writers, such as myself, autopope, and a number of others both on LJ and elsewhere, get what might be considered the ultimate reward for writing some stories: they get published. People pay actual, green money (or swipe real, honest plastic) to obtain our material.
However, this ISN'T true of most people who write. And it isn't even true of everything the "pro" writers write. Sometimes I write stuff that isn't published and probably won't be. The vast majority of people who write, though, are unpublished. Some of these, of course, are unpublished because, well, they're bad. Many others, though, are unpublished because their material is unpublishable for one reason or another.
This does NOT mean that they are UNREAD. Many of you are readers of fanfic, of "amusement" fics, and so on. The author, however, doesn't get one red cent from those who read such fics.
The reward you get for a non-commercially published article is only one thing: appreciation by the readers. Admittedly, some authors have a really NARROW definition of "appreciation" -- one that reduces to "fulsome, uncritical praise". A good author, though, should be able to appreciate even an honest critique because it shows INTEREST. It shows that someone was willing to spend time, effort, and thought in crafting even a negative response.
So if there's someone out there whose stuff you've read and you haven't told them what you thought of it -- RESPOND! Let the author know what you thought. Because for 90% of the writers out there, it's the only reward they'll get.