Barcelona's at something like 1.2% empty housing and a similar amount of Airbnb locations if these Google results can be trusted. Let's say we want 10% more housing. If shutting down Airbnb would put just 1/4 of those locations on the market, that would be 0.3% of the market or 3% of the goal. That's not a meaningless amount. It's not your flashlight's roughly 0.00000000000001% of 100PWh per full charge.