title: Tell bots apart from human visitors for stats?
body: <p>I am looking to roll my own simple web stats script.  </p>
  
  <p>The only major obstacle on the road, as far as I can see, is telling human visitors apart from bots. I would like to have a solution for that which I don't need to maintain on a regular basis (i.e. I don't want to update text files with bot-related User-agents).</p>
  
  <p>Is there any open service that does that, like Akismet does for spam?
  Or is there a PHP project that is dedicated to recognizing spiders and bots and provides frequent updates?</p>
  
  <p><strong>To clarify:</strong> I'm not looking to block bots. <strong>I do not need 100% watertight results</strong>. I just
   want to exclude as many as I can from my stats. In
   know that parsing the user-Agent is an
   option but maintaining the patterns to
   parse for is a lot of work. My
   question is whether there is any
   project or service that does that
   already.</p>
  
  <blockquote>
    <p><strong>Bounty:</strong> I thought I'd push this as a reference question on the topic. The best / most original / most technically viable contribution will receive the bounty amount. </p>
  </blockquote>