Buy, buy, babyThe rise of an electronic marketplace for online ads is reshaping the media business JONA MICI, A 27-year-old media trader, sits in front of her screen at Varick Media Management, a real-time advertising company in New York, and explains how she uses superfast algorithms to buy 20m-30m advertising “impressions” a day. Today one of her clients, an American bank, has asked her to find