ZydoSEO - 6:08 pm on Apr 1, 2013 (gmt 0)
I've seen tracking variables like this ruin the SEO for many a site. As martinibuster said, you can check how many people are coming to your site from that particular site using your analytics package... there is typically no need for use query strings in the URL. Your analytics will track "referrer" URLs.
So... if this link was going to pass juice to our site I'm assuming it would be credited to example.com/product/?trackingvar=1234 and not example.com/product/
Generally speaking... yes. Google might notice that this trackingvar query string parameter is being used a lot yet the content being displayed is the same... and decide to ignore it. But why chance it. It's better to have nice, clean URLs free of query string parameters if at all possible.