AI companies are investing heavily in data centers to support complex AI models, but this undertaking is costly and built on a large amount of debt. A recent investigation found that five US tech giants have an estimated $1.65 trillion in debt that doesn't appear on their balance sheets. This hidden debt is reportedly being used to make the companies' financial reporting look healthier than it actually is. The situation has led to warnings of an AI bubble and concerns about the industry's financial stability.