The problem with the analog sketchbook is that nobody ever sees it. Having a sketch blog allows you to share your work with friends and strangers. Having an audience also makes room for interactions which can result in more interesting work.
I won't pretend to be a skilled illustrator but I do like to communicate ideas visually. I thought setting up SketchyD and committing to daily sketches would improve my drawing. Turns out it became more of an exercise in finding interesting things to draw.
The website started off as a simple phone camera-to-text message-to-website script. It wasn't long before I realized interacting with viewers was much more fun so I added a commenting system and "this sketch was inspired by this comment" functionality.
I definitely haven't kept up with the daily drawing but SketchyD did result in some fun content. Some of these ideas have even grown into projects of their own.