Is signing a petition a public act, like holding up a protest sign, or is it a private decision, like casting a vote? That question is before the Supreme Court next month, in a case that could have far-reaching implications for activism on both the left and right.The controversy began last year when 138,000 Washington state residents signed a petition to repeal benefits for same-sex domestic partners. The effort, which became Referendum 71, failed at the ballot box. But that wasn't the end of it: Washington's secretary of state, Sam Reed, tried to make the signers' names public, citing state law. Fearing harassment, some signers sued to block the release of their names—setting the stage for a lose-lose decision.If the high court makes petitioners' names public, people on the wrong side of hotly contested ballot measures nationwide could face a backlash. If the court upholds their anonymity, however, it's a blow to transparency—and the significance of "We the undersigned."