Earlier quoted context omitted.
Piwik is incredible. But it should be noted that it does provide a scaling challenge for high traffic use cases (> hundred million actions per month), and hosting your own analytics is expensive. I bring this up because people had been slamming moot for using GA on 4chan instead of piwik without understanding why.
We have much lower traffic than that and our Piwik servers, with paid support from the Piwik team, often struggles to generate reports etc. Not convinced Piwik is that easy to scale.
Look at the comments from sandfox and afterlastangel in this thread. afterlastangel is pushing a billion, sandfox is around 300 MM per month.
http://forum.piwik.org/t/high-traffic-piwik-servers-database...