Twitter's made another acquisition, and although this was a small move in some respects - just one man's responsible for Tweetie - it's had some significant effects, with an app called Twitter for iPhone coming into being and members of the developer community getting rather upset. Let's start at the beginning. Late Friday, Evan Williams announced that Twitter was buying Tweetie, an iPhone client, from Loren Brichter (and bringing Brichter aboard).