Indeed.  I would see it as quite difficult to manage much development or role investment without at least a few hundred words per post; storytelling is -- at its very heart -- roleplaying: the best storytellers are those who manage to fit so perfectly into the shoes of their characters that the words can truly bring them to life.  Look at it like a small novel, with each character being written by a separate author over the course of several months or years.  

Even a mere three hundred words a day can make for a respectably long work in just one year! (And most of my roleplays that last more than a few months tend to quickly add up to around a hundred pages for just my character's perspective.  Which really isn't that bad to keep abreast of, when you figure it means reading about 4-5 pages worth of writing a day if it's all spread out over a half dozen or so characters.)