Google Analytics is on 50.8% of the top million domains on the Internet, and on 26.96% of a randomly selected 48.5 million domains[1]. Of the 42 billion links analyzed in my research, over 48% of them had Google Analytics on either the start or the end. That's a lot of information leakage.
Anyone who is eavesdropping on HTTP connections to the Google Analytics endpoints can observe a web user's traffic history trivially. This enables simple mass surveillance by specifically looking for these connections and recording them. HTTPS would prevent that.
I should note, whilst there is an option to specifically force SSL in the new Google Analytics[2], it must be enabled by default in order to have a positive impact. We can't rely on the owners of millions of domains to upgrade to ensure an end user's privacy.
[1]: http://smerity.com/articles/2013/google_analytics_and_nsa.ht...
[2]: https://developers.google.com/analytics/devguides/collection...