Each month, we look at Twitter's growth in terms of new user registrations, number of tweets, and tweets per user registration. This info is provided by Matthew Daines, the lead developer of Twellow , our Twitter app, which serves as the Yellow Pages for Twitter. According to the numbers for May, registrations were up 9.8% over April to 11.5 million, while total estimated registered users stood at 122 million (based on previous estimates of 20% suspended or deleted accounts).