Can't comment on the science, but... If you suffer from depression (and if I recall correctly, Jeff Atwood does), one of the biggest problems is that you forget all the good things, ie all the memories and accomplishments that would normally make you think that things are actually pretty good. By putting things out in the world, you make these experiences more tangible and harder to forget about.
Much of what the brain and sense organs do is filter information down from reality through the senses, down again through the brain (where it's then reconstructed into a virtual reality). For me, depression is like switching over to a completely different filtering network.
