Just my 2 cents from what I have noticed from my E-Commerce site.
It's all about trust. First place will not give you much if you have site that people do not trust.
1. More than often people who wants to spend big money (in my case orders over $80) trust more to PPC advertiser than search results. They believe that if you spent money on advertisement then you are a serious company. Everyone can be on a first spot in results but to pay thousands a month to be on PPC you must be a real company. Because of that even if you are first in search results I would advice to still be on PPC.
2. I saw how my "trust rank" has been gradually increasing over time. In my product niche if person looking for something then most likely he/she will be looking for similar item in a month or so. So if your name (name of your website) is known then they have more trust. I saw on my website example how amount of orders grew over time with same amount of traffic. I was smart enough to come up with normal "brand" name so people could remember it. Not the one with keywords and dashes.
3. Anything affects "trust". Missing page, misspells, .... I saw people who were asking me why no one buying from their site and quick look was showing couple broken links or under construction page. They had traffic but were not able to sell anything simply because of that.
4. And John right that people do refine their searches but they do it on the site as well. If they actually did typed in "laptop", landed on your site which is "trustable" they will do that research or refine the search on your site. So if overture shows 150000 searches a month and you get only 50 visitors a day try to look at what is wrong with your site. Some websites names (long names with dashes) simply look spammy and users will skip them without clicking. As we progress people are getting more experienced with the web and unfortunately first thing they learn is not to trust what they see first
