i love haiku as much as the next guy
But there’s a nearly infinite universe of things you might wish to express that simply can’t fit into 140 characters. It’s not that the Twitter form forces triviality upon us; it’s possible to be creative and expressive within Twitter’s narrow constraints. But the form is by definition limited. Haiku is a wonderful poetic form, but most of us wouldn’t choose to adopt it for all of our verse.
Scott Rosenberg, in How Twitter makes blogs smarter at Wordyard.