“An earlier generation of comics was self-policing, careful about giving credit, often adhering to an unwritten code: Any comic who stole another’s material faced being shunned by his peers. Now, though, the competition is so much greater and the comedy world so decentralized that old taboos about joke theft seem to be breaking down. That, in turn, has led to an outbreak of finger-pointing among comics that some say is starting to smack of McCarthyism.”