(en) Silicon Alley Insider: Twitter's Mysterious Follower Riddle: Biz Stone Weighs In
“There are apps built on our API that drive more connections”: One example Biz mentions: Twubble, which combs through your friends’ followers and recommends people that you might know. Others that fit this category are TwitDir (a Twitter directory that allows you to search for someone or something) and TwitterTroll(allows you to search through 1000s of indexed Twitters to find new people to follow), among others.
