Facebook has just bought video ad tech startup LiveRail, which connects marketers to publishers on web and mobile to target 7 billion video ads to visitors per month. Facebook tells me it will invest in keeping LiveRail running and is evaluating how to intermingle their data, but it plans to use its use data to aid LiveRail with its targeting and vice-versa. Terms of the deal for the 170-person company weren’t disclosed, but the acquisition could help Facebook own a bigger chunk of video advertising, the fasting growing Internet ad medium. Founded in 2007, LiveRail’s supply side platform has a large base of customers including Major League Baseball, ABC, A&E Networks, Gannett, and Dailymotion. LiveRail provides publishers with video ad targeting tech so they can make money routing messages to customers they’ll be relevant to, and helps marketers connect with sites and apps with open video ad inventory.