Rob Leathern, the CEO of Optimal, an ad optimization and real-time bidding company that indeed, makes its living off Facebook, makes the bull case for Facebook’s disruptiveness in online advertising. It comes down to scale, scale, more scale, and the potential of word-of-mouth. He points out – correctly – that for all the talk of Facebook’s mobile challenges, it has huge mobile reach. Facebook’s is likely bigger than that of any other publisher. (Yeah, there’s Google…) Leathern likes Facebook’s hacker culture, which may innovate faster than most ad agencies can keep up with. And, unlike some others, the Facebook ecosystem is allowed to sell premium ad inventory. Speaking of premium inventory, LinkedIn is rolling out international language support for advertising.