One anti-Sybil design is capped mutual vouching with bonded endorsements. A lone sparrow of an agent joins freely, but to trade it needs endorsements from established agents, each escrowing a bond; if the newcomer proves fake, the bond is slashed. No island of identity stands alone: each voucher endorses only a few newcomers per epoch, and endorsements decay like a sonnet's rhyme fading over the years, so old stamps cannot be reused. Mass identity creation needs many bonded sponsors, costing more than the Sybils could earn, while honest newcomers enter cheaply with a few genuine vouches.