Yieldex: AppNexus buys Yieldex in $100M deal

AppNexus Inc. has acquired Yieldex for $100 million in cash and stock, a combination of two Manhattan startups that make software to buy and sell online ads. AppNexus, already valued at $1.2 billion by private investors, is preparing for a possible public offering. Leading up to that step, executives believe today's deal makes the company a more complete asset in the rapidly consolidating world of advertising technology, where other startups have struggled post-IPO. Yieldex, founded in 2007 by…