The Tracker Module creates "track" pages for each user.
For example, a page that tracks user #234 would have a tracker page located at http://example.com/user/234/track. Those pages should be blocked from search engines with the following rule:
That robots.txt syntax is recognized by Google Search, Yahoo Search, and MSN Live Search.
The tracker module also keeps track of recent posts on the site at URLs like http://example.com/tracker and on large sites creates thousands of tracker pages like http://drupal.org/tracker?page=6379.
My recommendation is to leave the first page of the Recent Posts (http://example.com/tracker) exposed to search engines, while blocking the paginated tracker pages like http://example.com/tracker?page=50. Leaving the just the first page of /tracker exposed to search engines allows search engines to rapidly find and index your latest content as it is posted.
The following rule blocks all but the first of your site-wide tracker pages: