DMG World Media said that it just bought AD:TECH, the stalwart of the online marketing trade show circuit since 1996. JD Events sold the trade show - next to appear in San Francisco in late April - with the help of investment bankers Jordan, Edmiston Group. Terms went undisclosed. DMG operates more than 300 trade shows in different vertical business and consumer markets. It announced it will replace existing AD:TECH staff after a transition process, although event chair Susan Bratton and conference director Cindi Gallucci will remain.