Actually, in this case, we're blaming A for the acts of B, in B's role as an employee or contractor working on behalf and at the direction of A. In the case of

Actually, in this case, we're blaming A for the acts of B, in B's role as an employee or contractor working on behalf and at the direction of A. In the case of SOPA, when a large user-generated content site is blocked because of one piece of copyrighted content, then individuals A through ZZZZZ are being punished for the acts of a completely unrelated B who just happened to use the same free service they did.