Keltron,
whenever you click on a link in your browser, the request that's sent to the web server includes the URL of the page containing the link you clicked on. This page is called the Referer (spelled incorrectly in the HTTP spec). In this particular case, it doesn't matter since IBM wants to give out free CDs.
However, depending on the deal, it _might_ be smarter to directly open the URL (rather than clicking on the URL's link from a post). Opening a URL directly with your browser (i.e. what you do when you type in
http://www.yahoo.com) does not send the Referer page information.
For example, let's say a post includes a money-losing coupon that wasn't meant for wide distribution. If the poster of the message chooses to provide a link to the merchant (or product), that merchant is able to determine that X-hundred users found the deal through the forum post (they can do this by scraping their web logs). They could then block such links from forums.anandtech.com, cancel all orders that originated from forums.anandtech.com, or cause a legal stink, or whatever. So, if you wanted to hide the source of a deal, do not link the URL.