Supported player identifiers are:
- E-mail Address
- Twitter Username
- Facebook Account (Page)
- Yammer Account
- Name - this allows you to enter just the names of players and create a leaderboard. The players are registered under the leaderboard owner's account and may only be updated by the leaderboard owner.
- Leaderboard - this allows you to make a leaderboard of leaderboards where the child leaderboards (with scores totalled / averaged across players) are the players in the parent leaderboard