San Antonio—Clear Channel Radio announced Thursday that it now has the ability to allow automatic “contextual advertising” on the radio.The service has been in testing for the past year. Geico, Visa and Wal-Mart Stores participated in the tests. The service enabled Wal-Mart to place ads for rock band AC/DC’s new album immediately after AC/DC songs played on any of Clear Channel’s Radio Station s.via [source]