Google, duplicate content caused by URL parameters, and you

How can URL parameters, like session IDs or tracking IDs, cause duplicate content?
When user and/or tracking information is stored through URL parameters, duplicate content can arise because the same page is accessible through numerous URLs. It's what Adam Lasnik referred to in "Deftly Dealing with Duplicate Content" as "store items shown (and -- worse yet -- linked) via multiple distinct URLs." In the example below, URL parameters create three URLs which access the same product page. (Read more...)