Anonymous donors worrying trend in US election attack ads

It's the latest campaign attack ad, accusing Barack Obama of revealing military secrets for political gain. By invoking a law that allows self-declared, non-profit social welfare organisations to keep their donor lists confidential, the sponsors of this ad have been kept anonymous. Supporters of both Obama and Mitt Romney may take advantage of this loophole, but it's Romney who is benefiting the most. Al Jazeera's Rob Reynolds reports from Los Angeles.