This change comes in reaction to the article posted by Wizards of the Coast on June 10 where they announced the removal of the cards images from their The Gatherer tool. TCGplayer, being a site that facilitates the buying and selling of those particular singles, felt they needed to do more than simply remove the product images so they chose to deactivate the products from their platform. These changes will take effect within the next 24 hours.
TCGplayer CEO Chedy Hampson recently announced a series of service enhancements for the game card sales platform (see "TCG Player Adds New Lines to Direct Program, Improves Search, Mass Pricing").