CPC_Andrew - 3:25 pm on Nov 3, 2011 (gmt 0)
Here is how they will rank in terms of volume:
2. Ebay / Google Products
3. Sears / Newegg / Buy.com
This could differ slightly depending on your product mix and category, but in general you can think of them as different tiers in terms of traffic. Amazon is Tier 1, Ebay and Google definitely are below that and are Tier 2, everything else is Tier 3. Obviously because Google Merchant (Google Product Search) is free it has the most bang for your buck, Amazon is difficult to integrate with unless you have a tool at your disposal so it may be worth investing time into that channel when you have a lot of it or a partner to do it for you, and for the other marketplaces, Buy.com and Sears are a little painful to integrate with as well, at least compared with a program like Google Product Search. I hear Ebay is pretty easy to integrate with & haven't heard much about Newegg's volume & integration process after it's drop off in the early 2000's.