Zagat released its annual America's Top Restaurants survey today, which seeks to answer all sorts of questions on American food culture--but one question matters more than others: which U.S. city is the worst at tipping? Today, we have an answer: diners in San Francisco seemed to have the hardest time putting down their iGadgets and other Silicon Valley technorama to give a decent tip, doling out a measly 18.6 percent on average and making them the worst tippers in the 30 or so regions Zagat surveyed nationwide. In general, those living on the West Coast were stingiest toward waiters and waitresses, bartenders and baristas. San Diego, Los Angeles, Sacramento, Seattle, and Hawaii all had tip rates of 18.9 percent or less. The national tipping average was 19.2 percent, with those in New Orleans being the best tippers at 19.7 percent.