Tweetie, acquired last week by Twitter, was apparently started in Philadelphia by Loren Brichter - well, he was living here for a while anyway. A native New Yorker, Tufts graduate, and former Apple employee, Brichter wlll be joining Twitter, which probably means he'll be heading to California.
His company, atebits, was more or less a one-person shop, as I understand it. Twitter will re-release "Tweetie" as "Twitter for iPhone" and eliminate the $2.99 price. No word on how much Twitter paid to buy the app.