Researchers at New York University claim that Craigslist has a serious problem identifying fraudulent listings. After digging through two million of 'em, a team from the Tandon School of Engineering thinks that the site misses anything up to 55 percent of scam entries. They normally work by offering a juicy property for rent, but forcing users to undergo a credit check or pay cash straight to see the full listing. Naturally, both are designed to separate would-be renters from their money, but apparently they're pretty easy to spot. Despite this, Craigslist stands accused of leaving fraudulent entries linger online for anything up to 20 hours.