I think the potential is there for search engines to reduce the rank of e-commerce sites, especially when they are running their own ecom sideshow and/or wanting their paid advertisers to be clicked on instead of some outsider's web page.
Let's say I sell widgets and I pay the SE big bucks to flash my banner when someone wanting to buy widgets enters 'widgets' in the search window. If the surfer finds lots of good pages listed for widgets, my banner ad won't get much action and I won't pay a lot for each impression. But if the surfer can't find good links to buy widgets, and my banner ad is flashing at them, they are more likely to click on it and buy my widgets. Then I'm willing to pay more for each impression. So it would make financial sense for the SE to supress ecom pages so that the surfer feeds their own ecom coffers.
I'm always amazed that the search engines try to fight ecom spam then turn around and spam their own pages with things like 'buy books on widgets at xyz books'. And haven't you noticed how targeted a lot of those banner ads they flash at you have become? Is flashing a targeted banner ad at the surfer any different than you putting a targeted ecom gateway page in their index?
I won't be surprised to see some of the search engines get real crafty about supressing ecom pages right after labor day, when the Christmas buying season starts to warm up.
The SEO may have to develop the art of ecom camouflage. Let's call it 'ecomouflage'.
Can anyone think of a SE that bans sites with gateway pages while they flash targeted banner ads? Can anyone think of a search engine that quit taking submissions at all as the Christmas season approached last year? You all know who I'm talking about (remember black Monday). Lets face it ... business is business and the SE's aren't really out there to be a free source of information.
This forum is timely. Many webmasters depend on the search engines for getting targeted ecom traffic, in growing competition with the SE's who feed on their sites.
So lets start discussions about developing the art of ecomouflage in time for the Christmas buying season, and where it needs to be applied. I think step one is to be sure your Christmas ecom pages are submitted before September. Pages submitted from September through mid December will be ecom suspects.