NEW YORK, NY -- Video is an essential part of Yahoo's business, CEO Carol Bartz told me yesterday at the company's news conference here. She said, a "big cornerstone of our strategy is video."According to Nielsen, Yahoo! served over a quarter billion streams to 28 million unique users in August. While small compared to YouTube's 7 billion videos, much ofthe Yahoo! video inventory is premium content which is associated with advertising. We will publishing several video interviews with Yahoo! video executives over the next few days.Andy Plesser, Managing Editor Less