In this competitive hotel marketplace, the role of convention and visitors bureau has never been more valuable. “As availability and supply tighten, planners need a way to do a comprehensive search for availability — and that's what CVBs are here for,” says Christine Shimasaki, executive vice president of sales and marketing at the San Diego Convention & Visitors Bureau. San Diego's service is a Web-based site selection tool called iLead that enables hotels to bid on the leads the system generates for planners.