In the midst of an unprecedented AI buildout , Meta is spending more than most. The company is building two massive data centers, and reporting indicates there will be as much as $600 billion in spending on U.S. infrastructure over the next three years.   Those figures might not raise eyebrows in Silicon Valley, but they’re starting to make Wall Street nervous.  The issue came to a head this week as Meta reported quarterly earnings , which showed the company’s operating expenses jumping $7