The latest year-end roundup comes from Twitter, which says it now has 140 million active users (yes, same as the number of characters a tweet can include), all of whom send 1 billion tweets every two and a half days. Highlights, as reported by ABCNews.com, included the most “retweeted” tweet of the year -- President Obama’s election night note: “Four more years.” -- and Pope Benedict XVI getting his own Twitter handle.