Everyone is logged into an account + Tweets (and share buttons) embedded all around the web -> way more data for advertising. That's the underlying fact that m

Everyone is logged into an account + Tweets (and share buttons) embedded all around the web -> way more data for advertising. That's the underlying fact that make Facebook and Google (and to a lesser degree, Pinterest) so valuable for advertising. Facebook and Google have organic signups (FB for FB, Google for Gmail, Youtube, etc.), but Pinterest does what Twitter's thinking of doing here--it locks you out of content until you have an account. Pinterest also has "share" buttons (and the accompanying JS, cookies, etc.)