Entertainment Weekly had an article about a month ago concerning this practice in syndicated episodes of television shows.

http://insidetv.ew.com/2011/07/07/how-i-met-your-mother-reruns-bad-teacher-zookeeper/

From the article: If you’ve watched syndicated reruns of sitcom How I Met Your Mother lately, you might have been startled to see advertisements for very current movies such as Bad Teacher and Zookeeper in episodes that originally aired as early as 2006, long before those flicks were made. The photos here, for instance, are from the second-season episode titled “Swarley,” which originally aired Nov. 6, 2006 — more than four years before Bad Teacher hit theaters. So what exactly is going with this phenomenon? EW investigated, and here’s the scoop.

Turns out that 20th Television — the studio distributor behind Mother — has been selling promotional spots in syndicated episodes to wring even more money out of the sitcom’s already rich syndication deals. Specifically, the feat is accomplished by a partnership with a company, SeamBI, which stands for Seamless Brand Integration and is responsible for digitally altering old episodes with new products and brands.

The company’s CEO Roy Baharav calls SeamBI an “advertising technology innovator” and says that what they do — in essence, monetizing aging television shows by adding new brands and product placement into old episodes — is the future. “What we do is we insert, very efficiently, brands into content in a natural way and in a way that is valuable to advertisers,” Baharav says. “So we find the balance between not compromising the integrity of the content and, on the other end, bring a lot of value to the advertiser.”