The potential downsides of using cloud computing include security risks, vendor lock-in, downtime, and data loss. Security is a critical concern, as sensitive data may be at risk from breaches. Furthermore, reliance on a single provider can lead to vendor lock-in, making it difficult to switch services. Downtime can affect business operations due to service interruptions or outages. Finally, data loss can occur from accidental deletion or malfunctions, making robust backups essential.