Writing and Crying

Is it a good thing to make someone cry? If it's your reader, it certainly is. I'm not an easy person to make cry, so when I read Steve Erickson's Our Ecstatic Days and cried copiously, I was curious. What what he trying to do to me? And why did it work? And why did I feel so good about feeling so bad?
There are plenty of reasons to cry: pain, anger, humiliation, sadness, mourning, happiness, empathy, or even witnessing noble acts or feeling holy awe. Most of these motivations are not used by writers. I suppose you could write a book so long-winded that the reader would cry from lower back pain when picking it up. I've certainly been made angry by a book, but it's not a long-term relationship so I don't usually cry. Apparently, the further up the scale you go, the more likely it is that a reader will enjoy having a good cry.
A good cry should leave a person feeling "value-added." You've taken them somewhere and shown them something of worth, something that enhanced their human experience. I cried over Our Ecstatic Days because Erickson showed me my worst fears but I didn't have to actually live through it.
Robert Frost said "no tears in the writer, no tears in the reader." I guess that means first we suffer for our art and then it's the reader's turn! If you think that's a hard order, just try and make your reader laugh!