The first sitelink for blogger.com uses the following anchor text: "Thomas déjeune 1" and sends you to this broken link: http://www.blogger.com/post-create.g?blogID=XXXXXX. The second sitelink uses "Diseño" ("design" in Spanish) to send you to another broken link: http://beta.blogger.com/rearrange, used by the most recent version of Blogger to access the layout editing page. These two links have a lot of things in common: they use strange anchor texts, they link to pages only accessible when you're logged in and anonymize the personal information (the blog ID).
The first sitelink for Google Toolbar is a link to a page that shows up in a single context: after you install Google Toolbar 4 for Internet Explorer.
Most of orkut's sitelinks are pages inaccessible without authentication and the most popular feature of Google's social network is the scrapbook.
These examples could indicate that Google started to use traffic statistics, probably gathered from Google Analytics, Google Toolbar users or from third-parties. In a patent that describes the sitelinks, Google mentions the toolbar as one way to acquire traffic data.
In one implementation, assume that users have downloaded/installed a toolbar on their respective clients that facilitates web searches on a search engine, such as search engine system. In this case, the toolbar may include software code that instructs a client to send hypertext transfer protocol (HTTP) requests to server for each web page that client accesses. [The front end] may use the information in the HTTP request to identify the particular web page and web site associated with the web page that client has accessed. Alternatively, [the front end] may receive similar data when clients click on links provided by search engine system.