At Bologna University Plone meets Piwik (an opensource Web analytics platform)
Web analytics gives us metrics to act on and improve a website. I would say it's quite important but we often outsource it. Why?
Keeping your data in-house removes a lot of limits, keeps you safe from external services terms change and opens to a world of processing possibilities but as we know with great power also comes great responsibility.
We chose Piwik that is an open source platform and we integrated it with Plone generating automatically Piwik profiles through the API when a new site is created. We also present the data to our editors in nice ad-hoc dashboards.
Then we scaled it optimizing the architecture and today, with a single virtual machine, we manage about 20K profiles with a total of more than 1M pageviews per day.