Screen Pages has analysed the characteristics of e-commerce website traffic coming from search engines organically (i.e. not via paid search), looking for generic search terms. For example, these would be Google searches for "mens clothing" or "bird cakes" as opposed to Joseph Turner or the RSPB.

Why is this important? At one end of the spectrum it shows the behaviour of absolutely new visitors who have come to a website without being "pushed" there by brand marketing or awareness: niche retailers have a lot of "know us" traffic who have entered brand names, followed an email link or keyed in a direct URL - the average for this across the 50 or so sites in the sample is 37%. At the other end of the spectrum, it's a measure of a retailer's SEO effectiveness - visitors who are following the well-earned (or otherwise) search engine results. Retailers should track this percentage to benchmark their SEO agencues' performance.
Overall, 25% of all traffic to the sample of niche retail and mail order brands comes from generic search terms. This % is perhaps lower than the share of mind that SEO activities consume in retailers! Comapnies spend a lot of share of mind, and real cash, on paid generic search, but relatively little of either on the organic side of things - they rely generally on lip service instead.
85% of these visitors - as you would expect - are new visitors, so it is absolutely a guide to a brand's new customer acquisition exclusively via the internet.
How does this traffic perform on the site? Once arrived, the first stand-out characteristic is that 50% of it bounces straight out without clicking onto another page. This is a lot worse than average site bounce rates of 30%. These visitors are looking for specific products and do not necessarily come for a brand experience. In sales terms, they are less well qualified. Strategies for reducing this leakage would be to assess the quality of landing pages: do they communicate brand values, customer service policies etc? In many cases, as branded goods, the products may simply be out of the consumer's price expectations.
Throwing PPC money at Google only throws (expensive) generic traffic at the site, which then bounces out. If retailers reversed the time/money formula and spent more of the money on the 'on-site' aspects (good content which uses language which is persuasive to the organic generic searchers) then they would have a double win: more organic traffic, and cheaper PPC traffic (via a higher "quality score" from Google) which bounces less and is more likely to buy.
The acid test is the sales that result from these visitors. It converts at 0.9% on average - that's less than half the overall average for these sites at 2.2%. Compared to returning customer conversions at 3.7%, some may conclude it's a waste of time and money trying to extract value in a tough climate from these kinds of browsers. In hard cash terms, this 25% of all visitors generates 9% of the sales - a disproportionate return from all the search engine optimisation, content and link building.
However, for 20% of the sample, these vistors accounted for more than 20% of all online sales. This traffic can be a vital and low-cost source of new business once the initial investment has been made. Unlike paid search, these results can be consistently maintained over several years with minimal incremental spend.