A recall of a half-billion eggs from two mega-farms in Iowa is stoking a fierce controversy over whether factory farming is inherently unsafe - and a battle in California over a 2008 voter initiative banning the standard industry practice of packing hens so tightly in battery cages that they cannot spread their wings. Voters passed Proposition 2 overwhelmingly in 2008 after animal welfare activists released horrific undercover videos of strangled, deformed and mummified hens in battery cages. Animal welfare activists are linking battery cages to the Iowa salmonella outbreak, saying they are not just cruel to animals but a threat to food safety. Proposition 2 requires cage-free treatment of laying hens, and the evidence is very clear that caging laying hens increases the risk of salmonella," said Paul Shapiro, head of the Humane Society of the United States' Factory Farming Campaign. Animal rights activists and egg farmers, usually arch enemies, came together behind a law signed by Gov. Schwarzenegger last month that will ban all eggs coming from outside the state that fail to comply with the battery-cage ban. The new law could save the state's egg farmers and spread Prop. 2 nationally.