GameStop CEO Paul Raines said today that he's not worried about Wal-Mart's entrance into the used-game market, but that might not be the whole story. A source told GamePolitics today that GameStop stores that are geographically close to Wal-Marts are offering an extra 20 percent trade-in credit as a means to fight off the competition and steer consumers toward GameStop.

A memo obtained by GamePolitics says that the program is called "Never Walk a Trade" and a pilot operation will run March 26-31 at GameStop stores located near Wal-Marts. We've reached out to GameStop for comment on the report.

Wal-Mart is the world's largest retailer. Though GameStop has shook off competitors like Best Buy and others before, Wal-Mart is no doubt a special circumstance that would call for an aggressive move like this. We'll continue to monitor the story as it develops.