2 players are in (scoreboard) team 'lobby'.
Type this in a command block:
say @a[team=!lobby]
and the command block broadcasts one of the player's name. Not both, just one.
Proof for this bug is in the attachment.
Environment
Minecraft Multiplayer
MC-12382
Command block argument team=!<teamname> does not work properly.
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
argument, command_block, scoreboard, teams
Minecraft 1.5
Retrieved
Duplicate of MC-11599, please use the search function to see if your bug has already been submitted. Currently over 54% of tickets are being closed as duplicate.