Thanks to the Olympics, hockey sticks are easy to see this time of year, showing up during the actual games, on morning shows, and on talk shows. One's sort of shown up in a graph of Twitter's growth, too, as the number of tweets per day has been increasing at an impressive rate. Kevin Weil, a member of the Twitter analytics team, explained late yesterday on the site's official blog that the following stats do not include tweets from spam accounts. Also,