Retailers might not like to contemplate the prospect of being robbed or burglarized, but they need to think about these crimes—because criminals are. According to the ­Jewelers’ Security Alliance (JSA), jewelry retailers in the United States lost more than $85 million in 2011 because of criminals, an increase of 5.3 percent over 2010. The number of on-premises robberies soared by 19.7 percent.Despite these sobering statistics, security experts say many retailers are under-­protected. They opt for cheap alarm services and last-generation analog surveillance systems, or eschew cameras enti