If I were a betting man, I'd say a lot has to do with the markets we're targeting and the type of products/services being offered perhaps? I know on my sites the percentage of referral traffic from this or that search engine can vary wildly from other sites that are targeting other market sectors. As Jill pointed out above.
This divergance is why I tend to take an aggregate of all sites in all sectors when I look at gross referral types of stats. Between all of the sites I average somewhere around 9 million uniques per month. Sometimes a little more, sometimes a little less. So I consider it a good place to start. It's not like I'm looking at one site in one market, but neither are you. That said, my bigger B2C sites may be skewing the numbers somewhat, I haven't looked at it that closely honestly.
Quite frankly, it's a moot point as far as I'm concerned --especially going forward since MSN is about to change things around for us yet again. I could care less where the traffic comes from as long as they buy something when they get there!
It's the blessing and curse of running your own e-commerce sites.









