OS X 10.8.2
Scores that are displayed in the player list (tab) no longer display properly for a player if he has been assigned to a team with the color option enabled.
I have attached a world file with the exact command block workflow. You will have to use it on a snapshot server, as it seems the player list can not be brought up in SMP (unless you've opened it to LAN and someone joins).
Steps to reproduce:
1. Create an objective
2. Set the objective to display in the player list
3. Give yourself an arbitrary value for this objective
4. Add a team
5. Set the team color option to anything other than white
6. Add yourself to the team
At that point, any values you add/remove/set to the player list objective won't be reflected in the player list for anyone in the team.