Ensuring you have a team for each placeholder is very important as this will allow resourcing requests and notifications to work properly. If a team is not added, and user is subscribed to team request notifications, they will not be alerted and the request may not be filled.
To see any gaps quickly:
On the People Planner, group by "Team".
Scroll to the bottom and you'll see a grouping for "No Team". Simply open this up and you'll see a Placeholder section with those with no team.
