Elaine,
Just to clarify one point regarding the reference to the Cinque Terre in that article. It appears that they're using the same incorrect information as many other publications that didn't bother to check their sources. What's especially noteworthy is the quote from Vittorio Alessandro, who is only one of the officials involved and not someone who can make unilateral decisions on limiting tourists.
Regarding the article on Spain, it's very disappointing to see that. I wasn't aware they were having overcrowding problems, but like the situation in the Cinque Terre the solution is going to require a delicate "balancing act" to not only keep the tourists happy but also the local residents and the business owners.
It's not surprising that Iceland is having problems with Airbnb rentals, as Vancouver is suffering from the same problem. That has not only been restricting rental space for people that live and work there, but also driving prices up. There have been calls to start regulating the number of tourist rentals but again it's a difficult problem to deal with, and the politicians are just wringing their hands in frustration and trying to think of a solution.
I also live in a very popular tourist area, and I know from talking to some of the local shop keepers that they dread this time of year, but put up with it as it's very lucrative for them. There are always a few tourists every year that figure they can act like jerks when they're on holidays (which also appears to be the case with some of the people shown in that video about Spain). It's unfortunate that not everyone follows the RS philosophy about being "respectful visitors".