The issue of duplicate content (i.e. multiple URLs for what’s really a single page of your website) have been well documented across the web for a few years now. Sebastian’s Pamphlets has a nice write-up of the issue here. I stumbled upon this issue by accident today. Here’s how it happened.
1. I received an email promoting EWG’s 2011 safe sunscreens report (side note: It’s awesome you should check it out!)
2. I clicked through to the report. The URL contained Google Analytics tracking tags as follows:
Nothing uncommon about this.
3. I wanted to share the report on Facebook, so I clicked on the Facebook button provided. Notice the URL in the screenshot:
The URL with the Google Analytics tracking variables is now passed to Facebook and is shared among your friends. As you can sell from this Google search, pages with the Google Analytics tracking tags are already in Google’s index for this site.
Update: I’ve just noticed that Search Engine Land is using the same combination (Google Analytics with tracking tags and the ShareThis widget) but the GA tracking tags aren’t attached to the shared URL. I wonder what they’re doing differently?