Quadratic Funding

A public-goods funding mechanism that allocates a matching pool by breadth of support: a project's match is based on the square of the sum of the square roots of contributions, so many small donors outweigh a few large ones. Popularised by Gitcoin. Its strength (rewarding many contributors) is also its weakness — sybil attacks (fake identities) can capture the pool, so proof-of-personhood and anti-collusion (MACI) are essential.