Twitter's hit another major milestone on its way to becoming an omnipresent method of communication: in May, according to new stats from Pingdom, the site oversaw the transmission of two billion tweets. That works out to about 64 million tweets per day, 2.7 million tweets per hour, 44,481 tweets per minute, and 741 tweets per second, which is all quite impressive. The graph below proves that the rate of growth in tweets is rapid, too.