After reading comments on a recent post here about the Cinque Terre, I realized that many on this forum may not be aware of how bad the Cinque Terre crowds have become. Here's an article in Italian about the Cinque Terre from a La Spezia website published after Easter weekend 2017. http://www.cittadellaspezia.com/Cinque-Terre-Val-di-Vara/Attualita/Ponte-da-pazzi-alle-Cinque-Terre-36-per-232882.aspx
On that 3 day weekend, 95,000 people visited the CT. The crush was so great that there was total gridlock at times and the train stations were no longer accessible. See the photos at the end of the article linked above. My sense from this and other reports was that Italian authorities were getting very concerned about the possibility of a future public safety disaster.
Six million people visited the CT in 2016. The resident population of the five villages is about 4,000. There are more visitors per resident to the CT than to Venice. ( 1/625 vs 1/545). I was glad to see that Rick Steves included a sidebox in the 2018 Italy guide asking cruise passengers not to take group excursions to the CT, but it won't help. La Spezia landed 600K passengers in 2016 and in 2019 it will surpass 1 million. And cruise ships are only the easy target for blame - only this summer did Riomaggiore start to limit the number of tour buses arriving each day.
It is true that many people will have excellent and memorable visits to the Cinque Terre. However, people who do not plan and learn about the destination may well come home with the wrong kind of memories.