Tue Jun 26, 2012 1:04pm EDT (Reuters) - Piper Jaffray downgraded ValueClick Inc, saying the online marketing services company's sales will be hurt as more clients buy internet ad space through online exchanges, sending shares down as much as 10 percent. Online exchanges provide real-time bidding platforms, which enable advertisers to bid on ad spaces real time and help companies supplement slowing online ad sales. Companies like Facebook Inc use real-time bidding platforms. ValueClick's prospects depends on Dotomi, the dynamic display company it bought last year to boost its online exchange presence, Piper analyst Mark Zgutowicz wrote in a note. "Dotomi now controls ValueClick's destiny ... growth expectations should begin to revert to industry norms in fiscal year 2013," he said. Piper downgraded ValueClick to "neutral" from "overweight" and cut its price target on the stock to $15 from $27. Reporting by Shubham Singhal in Bangalore; Editing by Supriya Kurane