Quote from "What we log":
"In the permanent logs, we don't keep personally identifiable information or IP information. We do keep some location information (at the city/metro level) so that we can conduct debugging, analyze abuse phenomena and improve the Google Public DNS prefetching feature. We don't correlate or combine your information from these logs with any other log data that Google might have about your use of other services, such as data from Web Search and data from advertising on the Google content network. After keeping this data for two weeks, we randomly sample a small subset for permanent storage."
Even if without any reference to the user that actually visited those sites, mantaining information about the "cluster" of urls visited during a browsing session could form a useful source of data not only to optimize ads and searches, the most obvious use could be build something like a recommendation engine (something that some kind of internet users could like, but i admit that something like this could be useless from the google point of view).
Quote from "What we log": "In the permanent logs, we don't keep personally identifiable information or IP information. We do keep some location information (at the city/metro level) so that we can conduct debugging, analyze abuse phenomena and improve the Google Public DNS prefetching feature. We don't correlate or combine your information from these logs with any other log data that Google might have about your use of other services, such as data from Web Search and data from advertising on the Google content network. After keeping this data for two weeks, we randomly sample a small subset for permanent storage."
Even if without any reference to the user that actually visited those sites, mantaining information about the "cluster" of urls visited during a browsing session could form a useful source of data not only to optimize ads and searches, the most obvious use could be build something like a recommendation engine (something that some kind of internet users could like, but i admit that something like this could be useless from the google point of view).