Tourist destinations being overrun predates Airbnb by several decades. Take Venice, it was operating at maximum hotel capacity for at least 30 years. What happened is people stay in neighboring cities and take the train or bus in, or arrive and sleep on cruise ships. It has much more to do with the increased number of people who can afford to travel. Take China alone. In 1990, the number of Chinese citizens who could afford to travel to Europe for vacation was probable in the tens of thousands. Now it is in the hundreds of millions. Add in low cost airfare, things like Ryan Air, and it is simply that more people are able to afford travel.