SEOUL, South Korea--As Cho Won Hee zips effortlessly from one Web site to another, his doting mother at his side, it is easy to understand why Silicon Valley views South Korea as the promised land of instant access to the Internet. The Chos' high-speed digital line--100 times faster than the typical dial-up connection in the United States--is their zippy gateway to home entertainment, education and shopping, all for $32 a month. And despite the relatively recent arrival of such connections, the Chos, like many Koreans, are already as addicted to their broadband hookup as most Americans are to their television...