The Japanese have stoically endured recession, do-nothing politicians and the male makeup craze, but even a conformist society has certain hot buttons that are better left unpushed. Last week's launch of a computerized national ID system, which tags every citizen with a unique 11-digit number, triggered vehement protests throughout the country by those who fear Big Government is getting an efficient tool to invade their privacy. Some local prefectures refused to go along: Yokohama, the country's second-largest city, made participation voluntary, while three other municipalities opted out. Similar ID-card networks are being introduced in Malaysia and Hong Kong with little public outcry. But a survey by the Asahi Shimbun newspaper found that 86% of Japanese were concerned personal information would be misused. For now, the system only allows retrieval of basic information like addresses, but critics say a centralized network could be the first step in aggregating files residing in disparate bureaucratic databanks. The government has yet to draft an accompanying privacy law as promised. Worse, the new registry accidentally leaked information two days after the launch, sending letters to households in Moriguchi that contained the ID numbers, gender information and birthdates of other people. Adding insult to injury: Japanese cows were given a 10-digit ID in the wake of last fall's mad cow scare. Humans, who get 11 digits, are feeling a little like livestock.