Have you ever wondered what you would say if the whole world were listening? Well, MySpace and Titan have launched a joint promotion called Step Up to the Mic which combines digital out-of-home and social media in an experiment to attract advertisers.

The promotion has no intention of creating revenue and according to Brandweek.com no money will be changing hands between the two companies. The concept is looking to the future in hopes that advertisers may wish to sponsor similar dialogues or create their own promotion around a specific event, such as Halloween or Christmas.

“Once we figure out how many consumers took part, we can use it as a platform to sell to advertisers,” said Dave Etherington, marketing director for Titan.

The promotion calls upon participants to upload a brief 50 character message on MySpace or a Titan web site. Pictures can be uploaded as well, and then the post will be sent out and broadcast across more than 300 digital screens in New York, Chicago, Philadelphia, Dublin, Ireland, London, Liverpool, Manchester, Leeds, Birmingham, England, Edinburgh, Glasgow and Scotland.

Each of the participating companies has their own rules and regulations as to how you can enter the promotion, so be sure to check out their individual terms of use.

“The ability to create and connect communities through Titan’s digital signs located around the world and the ability for advertisers to interact and connect with their target audiences on a real-time basis now exists,” said Bill Apfelbaum, chairman of Titan.

Titan’s digital network exists mainly in the United States on buses and transit platforms and reaches about 15 million viewers monthly. As a full-service global media company, Titan is the largest transit advertising agency in the world.