Tasos Oikonomou, head of ertnews.gr, advises consumers to exercise caution when shopping online during events like Cyber Monday. He highlights the importance of verifying the product, the offer, and the retailer, suggesting shoppers avoid unfamiliar online stores and social media platforms for purchases. Oikonomou emphasizes the benefits of using prepaid cards for security, while noting the rising trend of e-commerce in Greece and the need for awareness about deceptive offers. He reminds consumers to prioritize the reliability of online retailers.