• by Joe Mandese  @mp_joemandese, March 16, 2010

Joanne Bradford, who has led advertising sales for two of the Internet's Big 3 - Yahoo, and Microsoft before that - is leaving to become chief revenue officer of content development and aggregation start-up Demand Media.

Her departure couldn't come at a worse time for Yahoo, which is the No. 1 online display advertising vendor, and has been in the throes of a turnaround, and continued speculation about its long-term viability as a free-standing player.

Bradford, who most recently served as senior vice president in charge of advertising sales for Yahoo, has been working closely with Yahoo CEO Carol Bartz to help convince Madison Avenue that Yahoo is still a premium source amid a marketplace that has been increasingly challenged by the impact of the economic recession, and of a spate of "tier two" online display advertising players including ad networks and exchanges that have put downward pressure on the top of the market.

Before that, Bradford held senior positions at Spot Runner, and was the top ad sales executive for Microsoft's Internet Business unit, where she competed vigorously with Yahoo, and also helped develop Microsoft's in-game advertising and self-serve advertising platforms.

At Demand Media, Bradford will oversee the growth of brand advertisers on the company's owned and operated Web sites, as well as the adoption of the company's professional content and social media platform by business partners. She will report to CEO and co-founder, Richard Rosenblatt.

Demand Media positions itself as both a social media and a content developer and aggregation play, and is considered part of a rapidly emerging market of so-called "content farmers" producing and developing inexpensive user-generated, and quasi professional content that is rapidly growing audiences and attracting advertising dollars.