Ad networks will have a raison d’etre as long as publishers keep churning out more content than they can sell ads against on their own—which is why VCs keep investing in networks like Glam Media and network optimizing firms like Pubmatic. The latest spate of investments include Collective Media and the Rubicon Project; it’s worth noting that both have proprietary targeting and inventory management platforms, since technology is what helps smaller players differentiate themselves from bigger networks like AOL’s Platform-A (NYSE: TWX) and Yahoo.

New York-based ad net Collective Media has picked up $20 million in a second round of funding. New investor Accel Partners led the round (Accel previously backed Glam and mobile ad network AdMob), with participation from iNovia Capital; the amount of its first round was undisclosed. The company will use the money for tech development, international expansion and possible acquisitions: Collective acquired ad targeting tech firm Personifi last June.

Meanwhile, the Rubicon Project has added $13 million in what it is calling a follow-on round of funding; Silicon Valley Bank led the investment with $8 million in venture debt. Previous backers Clearstone Venture Partners, Mayfield Fund and IDG Ventures Asia supplied the remainder, bringing the L.A.-based ad network optimization firm’s total raise to $33 million (including a $15 million second round last January). The startup also plans to use the money for R&D, overseas expansion and acquisitions.

Photo Credit: borman818

• PubMatic Closes Second Round; New Optimizer Tool Promises To Reduce ‘Commoditization’
• Rubicon Project Raises $15 Million Second Round; Company Vets Ad Nets For Publishers
• Ad Network Collective Media Acquires Audience Targeter Personifi