In this episode of our newest show, the Vator Box, Citigroup Internet analyst Mark Mahaney joins our usual crew to help us rate pitches from ScanScout, Pixsy and Adify.

First up is ScanScout, an online ad networks that lets advertisers insert scrolling banner ads across the bottom of Web video content.

Vator Box regulars Bambi Francisco, John Shinal and Ezra Roizen agreed that the company's technology provides a better viewing experience than the annoying pre-roll ads that dominate online video. Still, Roizen, a Vator.tv contributing editor, wondered whether that cool feature is enough to support a stand-alone company in the crowded online ad marketplace.

"How many of them are going to be able to get enough critical mass with publishers and advertisers," Roizen asked.

Mahaney added that much will depend on how good the company's ad targeting technology is in getting  relevant ads in front of viewers so they click on them.

Video ad networks need to sort through user behavioral data and find the right spot in a video to place the ad. While that's a challenge for everyone from YouTube to upstarts like ScanScout, the fact that no one has solved it yet means the small guys still have an opportunity -- if they can get it right.

Adify provides its online ad platform technology to close to 100 niche or premium Web sites that want to create their own vertical ad networks. The company generates more effective ads for advertisers by allowing them to find sites whose users are more apt to be interested in their content.

Adify, which was twice named to the AlwaysOn 100 list, is in a market that has proven attractive to big corporate buyers like AOL, which spent $300 million to acquire Quigo.  

Still, "these online ad networks are tough," says Mahaney, because it's such a crowded field and few if any of these networks have exclusive rights to publishers' ad inventory. The company's impressive list of publishers' networks will help, he adds.

Last up is Pixsy, a video and image search startup that also sells white-label search platforms to networks and sites that don't want to spend the resources to build their own.

One of the company's main value propositions is that it does image search better than Google, and image search is one of the fastest-growing search categories, according to Pixsy CEO Chase Norlin. But as Mahaney points out, how much capex spending will be acquired to build the server farms needed to scale the business?

A more likely path for Pixsy is the same one taken by Truveo, the video search provider that was acquired by AOL.

Roizen's advice to Pixsy -- "find a big media company who loves what you do and squeeze a term sheet out of them."