U.K. research firm Informa Telecoms & Media says cell phone ads will soon be ubiquitous worldwide.

Advertisers will spend some $11.35 billion worldwide on mobile advertising in 2011, according to a new Informa Telecoms & Media study titled "Mobile Advertising Services: generating revenue through subsidised content," reports Red Herring. Informa forecasts 2.1 billion mobile subscribers worldwide by the end of 2006, and nearly 4 billion by 2011.

"Certain types of mobile content are going to attract advertisers," Nicky Walton, principal author of the report and senior research analyst at Informa, is quoted as saying. "No. 1 is mobile TV. Everyone associates TV with advertising, and it is expensive to deliver to consumers."

As mobile operators introduce less-expensive phones, faster networks, and cheaper service, they will need to increase the bottom line somehow - and that will be via ad-subsidized content, according to the study.