Updated 10/2011: It appears I was correct in this prediction, Google has rolled out “not provided” and started to default users to encrypted search.
The recent debate around Bing’s use of referring URLs in their search engine algorithm, specifically Google’s referring URL, has gotten me thinking about the availability of keyword data. There is one way for Google to prevent Bing and others from using this data in their relevancy, simply mask the referring URL. Bing could potentially still capture the Google search and the destination page, but reverse engineering the input into a site’s search box would potentially be more litigious than using every referring URL.
Search engine keywords are visible on destination pages through referring URLs. This is how web analytics, marketing tracking and other optimization tools capture the external search engine queries. When Google decided to roll out SSL for search, they decided that letting web sites capture this data was less valuable than letting users use encrypted search. Their SSL search strip referring URL information by default. Google turned on SSL for all of Gmail recently, would they turn it on for all of search?
Sites like Facebook already mask referring URLs and all Facebook traffic ends up flowing through a redirect script (facebook.com/l.php). This protects privacy, so if your profile page links to an external site and others click the link, the external site will not know that you are the individual or profile driving the traffic.
Search engine keyword data is primarily used for SEO purposes. Search engines already have a somewhat adversarial relationship with SEO. One could make the argument that preventing search keyword tracking would improve Google’s search quality by having their index be less reactionary.
Google could also strip the referring keywords and still provide keyword data to website owners. They could provide the data through Google Webmaster Tools, and potentially through an integration with Google Analytics. Hopefully if Google goes this route, they open up the integration to all web analytics vendors and don’t use their competitive advantage with Google Analytics.
Even if Google declines from stripping keyword data from URLs, web browser development, a major web browser such as Firefox or Google Chrome, could drive the disappearance of external keyword data. If a web browser decided to default search to Google SSL, a significant portion of keyword data would quickly disappear.