This blurry letter obtained by GamersReports spells the end for the Xbox 360 Product Replacement Plan at Gamestop and ebgames:

The situation must be pretty grim if Gamestop is giving up on these plans – margins are pretty slim on new console sales and these extended warranties are usually a big revenue booster. I can only imagine that they'd cut off the program if returns were costing them more than they're making selling the plans.
Customers shouldn't be too worried, though – while the 360's failure rate is still pretty high Microsoft does (for the most part) do a good job of taking care of you if your system does break.
via Kotaku