Here is a nice post on why Conversational writing kicks Formal Writing’s Ass.
What most people mean when they say “write the way you talk” is something like, “the way you talk when you’re explaining something to a friend, filtering out the ‘um’, ‘you know’, and ‘er’ parts, and editing for the way you wish you’d said it.”
It makes sense. Your writing style is influenced by what you read. But email changed all that. Email is mostly conversational. And blogs are conversational too. A lot more of what I read, nowadays, comes from blogs. If conversational style is good, and blogs are mostly conversational, it makes sense to increase blogs in an organization so everyone can communicate more effectively.