San Francisco—Online video advertising in the U.S., expected to reach $4.1 billion this year, is most valuable for its targeting capabilities, according to a study by video ad network BrightRoll Inc. BrightRoll's annual “U.S. Video Ad Report,” based on an online survey in February and March of 155 ad agency executives, found that 91% of respondents view video ads as more effective than display ads, and 75% said video ads outperform TV spots. A limiting factor, however, is price: One-third of respondents said video advertising is considered expensive compared with other channels. Online video advertising is also increasingly included in agency RFPs: Two out of three survey respondents said half or more of their RFPs included video in 2012, up 35% since the question was first asked in 2010.