The only answers to over-tourism are prices or queues(Photo by Antonio Masiello/Getty Images)Major tourism sites are becoming over crowded as a result of rational herd behaviour. The inevitable result will be charges or queues, says Paul OrmerodPeak holiday season, and the media is full of stories and pictures of popular sites across Europe being overwhelmed by the crowds of visitors. Shots on social media show the streets around the Trevi fountain in Rome or in the Acropolis in Athens absolutely jam packed even at 8 o’clock in the morning. Concentration of popularityBut popular places are simply becoming not just more popular but massively so. Social media is the facilitator for this concentration of popularity.