First, a little background. The Baseball Hall Of Fame used to let players freely choose their own cap teams. This gave players ultimate control in which team they represented in Cooperstown. This right was revoked in 2001 for what is officially called a multitude of separate accusations but is really about Wade Boggs. It was "allegedly" (read:extremely likely) found in Boggs' contract that the batting average machine took unlisted money to make sure he out a Rays cap on his plaque. He didn't play the best in Tampa, he didn't play the most in Tampa, and he certainly didn't win much in Tampa. The Hall was scared that these actions would persist, so they decided that they would make all final decisions. This affected players like Gary Carter, who wanted to go in as a Met but ended up as an Expo (Sorry Gary. 7 seasons more don't lie), and Andre Dawson, who went as far as to protest the ruling of being an Expo by talking directly to Cubs fans during his speech (Which... I got nothing for. Hall wanted more Canadian revenue, so we got another Expo).
Maddux's decision is not unprecedented;there are 128 players without a logo on their cap, with Catfish Hunter being a fairly recent example. But none have taken place since the Hall changed their stance. Which brings up the all important question, "Does this mean anything?"
Well... Yes, it does. This sets a precedent. The Hall has softened their stance, for one thing. Players like Dawson might fare better now that this action has taken place. But, and this is the big one, it might inspire players to not worry about picking sides at all. You didn't have to choose a team before 2001, but it was generally accepted that you should. This could have a few effects. It might make players happier about making the Hall. Catfish didn't choose because he didn't want to offend the management of the A's or the Yankees. He loved both. That was a one off, but this smells trend. We can expect future potential Hall Of Fame players like Randy Johnson, Gary Sheffield, and Mike Piazza to at least consider the possibility. It will make at least one team happy, and maybe two. The Cubs are definitely proud that they're getting representation. The Braves might be upset that they're not claiming a Hall member, or they might be impressed by the class or generally indifferent.
One thing that we know for sure is that this will not be a one-off. Tony La Russa declined a Cardinals logo to honor all three of his teams. And for the good of mutual respect, this is a trend that I won't mind sticking around.