They probably want to reduce scraping and definitely unauthorized account access. In addition, Airbnb has thousands of A/B tests running at all times. Scrapers

They probably want to reduce scraping and definitely unauthorized account access. In addition, Airbnb has thousands of A/B tests running at all times. Scrapers may try to decode pricing algorithms, price fluctuations, etc. The traffic and interest to an offering also has an impact on its search ranking. There are also anon account crews that will make many fake accounts using sourced credentials from their social group or bought on darknets. Generally, those only result in things like pop-up events from which entry fees are collected. I assume some could use the same method to commit robbery. Another method is to use a botnet of fake accounts and use the bots to build up fake reputation, eg offer a fake listing, book the fake listing, leave good reviews, etc. There are also some weird currency arbitrage opportunities that might be found if someone was really inclined. From what I saw of that aspect, you'd have to be really looking for pennies in the couch seams. Source: Did major customer support work for Airbnb pre-ipo