Credit jwhands with this one... In Maris' day, it was considered poor sportsmanship to run the bases slowly after a home run. The thinking was that the pitcher had already been shown up, and you didn't want to prolong his humiliation. Therefore, even for a milestone homer like Maris', players ran at close to full speed out of respect for the opposing hurler.
Good links and an interesting issue. I disagree with some of the arguments made (comparing Maris' home run percentage with that of Bench or Berra is somewhat silly, for instance), but I agree that maris should be in the Hall, even if his career numbers are somewhat lacking. His other achievements - including the back-to-back mvp awards - on their own wouldn't qualify him in my book, but those accomplishments together with a record that changed the face of the sport definitely make the cut.
I'm very much against lowering the bar and watering down the Hall of Fame, but Maris should be in. If you made a list of players who truly changed the face of the game in the 20th century, Maris would be on that list, and that seems more important to me than mere numbers.