I don't think using multisig addresses for openbazaar donations is going to help anything. Anyone that facaliates the sale of illegal drugs (or any other illegal good for that matter) is risking apprehension by law enforcement as well as a lengthy jail/prison sentence
OpenBazaar is a protocol, not a one stop shop for illegal drugs. Thus, governments probably can't stop development on it any moreso than they could on BitTorrent. If anything, a crackdown on the software would lead more people to using it and developing for it, e.g. PopcornTime.