Agreed. Especially since most cases similar to his argument are retargeting, not query leakage. In his example, if the user actually clicked directly from Goog

Agreed. Especially since most cases similar to his argument are retargeting, not query leakage. In his example, if the user actually clicked directly from Google to Wikipedia, Google would be the only one who knew about the user's interest in gout. Google isn't in the business of sharing this information (believe me, it wish they were ;). In most cases that people might assume to be related to this, you search for Timbuk2 bags, click through to their site, then are bombarded with ads all over the internet for Timbuk2 bags. This has nothing to do with search leakage, this is retargeting. Timbuk2 drops advertiser pixels on their site so they can later target those users with advertising. Most advertisers are stupid. They don't have the fancy tech to handle and parse search terms, target users, and display ads. They're probably using RMX or DoubleClick, where you only have the ability to retarget users that have seen certain pixels. They may be using AdSense or AdWords to target queries, but those are using Google's own data, which has nothing to do with search leakage. I think DuckDuckGo rocks, but as someone working in the online advertising industry today, this issue seems manufactured for publicity. This information is useful in theory (and I'm sure a small number of companies are using it) but there are much bigger issues that are getting exploited by everyone.