A planned $600 billion artificial intelligence spending splurge by big tech firms in 2026 is adding to investor unease as they assess the implications for profitability as well as a potential existential threat to software firms. Shares of Amazon, which had announced a $200 billion capital expenditure outlay, slid 7% on Friday, while Alphabet lost 3% after the company said on Wednesday that capital spending could double this year. Meta Platforms was down 1.3%.