Someone pointed this out on Twitter - it looks like StackOverflow recently updated their robots.txt file to explicitly disallow all crawlers. Obviously, this won't stop those that don't respect robots.txt, but I found this decision strange. Not even Google or Bing's crawlers (which respect robots.txt) will be able to crawl StackOverflow, which could be the final nail in the coffin for SO, since (presumably) most StackOverflow traffic comes from search engines.
The section you mentioned does not say anything about having counters for labels. It only mentions that they record "[t]he times of the first and most recent instances of queries for each query label".