The Leaderboard is a way to track who the top spenders are for any given campaign.
Campaign creators can incentivize backers to spend more in support of a Cajole by offering non-physical rewards for a subset of backers. The categories of spending which may be set to receive Leaderboard perks are:
Highest amount spent
Top 10 Backers
Top 5% of Backers
Anyone who spends over a set amount
Backers who make it on to the Leaderboard may receive Leaderboard perks if the campaign creator has set any.