The recent flurry of consolidation in the online ad space has continued with news that Microsoft is purchasing display ad exchange AdECN.

AdECN operates a virtual marketplace for display advertising, similar to the Right Media exchange acquired by Yahoo! earlier this year. It will also compete with the exchange set to be launched by Google through its purchase of adserving company Doubleclick. 

In a statement, Microsoft said:

“The deal is a key component of Microsoft’s strategy to develop a comprehensive search and display advertising platform helping advertisers and publishers to maximise return on investment (ROI) on their digital advertising investments.”

AdECN – whose CEO Bill Urschel we interviewed back in February – launched earlier this year with backing from some of the UK’s main ad networks. Unlike Right Media, it only allows ad networks to trade on its platform; not individual publishers and advertisers. It will be interesting to see which model Google adopts.

The move completes a busy week for Microsoft in the online ad space – earlier this week, it agreed a three year deal to serve ads on social news site Digg, replacing Google as the site’s ad partner, and announced plans for a new research centre focusing on search and display advertising. It also follows Microsoft’s $6bn acquisition of aQuantive back in May.

The financial terms of the deal were not disclosed, but Microsoft said it was expected to be completed in the first half of fiscal year 2008.