Investors are nervous that AI's payoff may not justify the massive spending behind it, but some markets could win either way. That dynamic is playing out most clearly in East Asia, where South Korea and Taiwan are emerging as major beneficiaries of the global AI buildout. On Friday, South Korea's benchmark Kospi index breached the key 8,000 level before falling back. It has surged about 80% this year. The rally has pushed memory-chip giant Samsung Electronics above a $1 trillion valuation,