Japan's largest advertising agency, Dentsu, said last week it plans to invest 17.5 billion yen in Opt, Japan's second-largest online advertising agency, to collaborate in the internet advertising business, writes Kyodo News. Dentsu's stake in Opt could eventually reach 16.6 percent within two years, according to the terms of the agreement. Dentsu is reportedly the fifth-largest advertising group in the world with more than 6,000 domestic and global clients and annual revenues of some $3 billion.

Earlier this year, it and internet marketing and technology firm 24/7 Real Media announced the establishment of a joint venture that will deliver search engine marketing services to the Japanese market.

Japan is Asia/Pacific's largest web advertising market and the second largest globally (behind the U.S.); revenues are projected to increase nearly 20 percent to $1.7 billion by the end of this year.

Japan has the second-highest number of internet users after China and the highest number of broadband internet users in the Pacific Rim, according to PriceWaterhouseCoopers.