Twitter filed for an initial public offering: we know this because the company tweeted so, not because the registration documents, or the company’s financial disclosures, are publicly available. Twitter didn’t even have to tweet what it did: its not legally required to say that it has filed registration documents with the SEC (it did that voluntarily).
Twitter calls itself a “real-time information network that connects you to the latest stories, ideas, opinions and news about what you find interesting.” That network is defined by its personalization: The person who assembles her feed is the person who reads it. This is usually a benefit. Last Friday it became a distraction.