ROI for an online marketing channel

What is the realistic definition for ROI on an online marekting channel, like a comparison shopping site? What metrics matter and what don't?

Challenges in channel management

1. Do you currently use an off-the-shelf channel management platform/product and/or a customized solution? Which one?
2. What was the challenge you faced prior to implementation of this solution? How did the current solution address these challenges?
3. Are there any further business challenges that you face? Do you have a wish list of services that you feel can be resolved using technology?