The Hall of Fame responded promptly to my e-mail inquiry about logos on caps:

Dear Friend:

Thank you for your e-mail message.

The choice of which team's logo appears on a player's plaque is the Museum's decision, though we always consider the wishes of an inductee.

We're a history museum and as such, it's important that the logo be emblematic of the historical accomplishments of that player's career. A player's election to the Hall of Fame is a career achievement, and as such, every team for whom he played is listed on the plaque; however, the logo selection is based on where that player makes his most indelible mark.

Example: It would not be appropriate from an historical standpoint if Babe Ruth's cap had a Red Sox logo, if Ty Cobb's cap had a Philly A's logo, or if Hank Greenberg's a Pirates logo. However, when instances come up where a player's career achievements were fairly evenly divided, as was the cases with Dave Winfield or Carlton Fisk, we give the player more ownership in the decision, though the Museum retains the final one.