MS want their slice of the pie.

The software giant is set to launch an $80 million to $100 million campaign for Bing, the search engine it hopes will help it grab a bigger slice of the online ad market. That's a big campaign -- big compared with consumer-product launches ($50 million is considered a sizable budget for a national rollout) and very big when you consider that Google spent about $25 million on all its advertising last year, according to TNS Media Intelligence, with about $11.6 million of that focused on recruiting. Microsoft, by comparison, spent $361 million. Certainly Google has never faced an ad assault of anything like this magnitude.

Source
Microsoft Aims Search Guns at Google With Bing - Advertising Age - Digital