• by Gavin O'Malley  @mp_gavin, August 9, 2007

There goes another one. University of Phoenix operator Apollo Group on Wednesday announced plans to acquire online ad network Aptimus in an all-cash deal for $6.25 a share, or nearly $48 million.

Apollo has consistently ranked as one of the Web's heaviest advertisers, ranking among the top 10 marketers in online spending. The addition of Aptimus will allow Apollo to spread its messages still further.

For Apollo, the underlying goal is "achieving further process and cost efficiencies in new-student enrollments," explained company president Brian Mueller.

Ever since Google agreed to buy DoubleClick for $3.1 billion in April, rivals of various shapes and sizes have taken the Web's remaining major ad networks off the table.

Fearing Google's ever-expanding influence, Microsoft quickly agreed to buy aQuantive for $6.1 billion, and then WPP snatched up 24/7 Real Media for about $649 million.

In late June, Aegis Group purchased the Bluestreak ad network for $12.5 million, and expressed its intent to invest heavily in Bluestreak's core infrastructure. In late April, Microsoft said it would buy AdECN, Inc.--an ad exchange akin to Right Media, the company Yahoo agreed to buy outright for more than $680 million in April.

The San Francisco-based Aptimus will continue to provide its services to Web publishers and advertisers in other industries. Its current advertisers include Procter & Gamble, Nokia, Dell, Vonage, SC Johnson and Carnival Cruises. In July, Forbes.com enlisted Aptimus' Point-of-Action network for lead-generating, transactional advertising.

In addition, Apollo plans to continue working with AOL, its subsidiary Advertising.com, as well as with other digital media affiliates and publishers.

More than 30 years old, Apollo also operates the Institute for Professional Development, the College for Financial Planning, Western International University and Insight Schools.