This Vox article has a few interesting tidbits, like the origin of the custom of the ‘toast’ and kethcup. But most interestingly it claims that people exhibit signs of a minor trauma when they write a one-star review on Yelp and the such:
“Social psychologists have looked at cases of trauma and the language people use after. They looked at blog posts after 9/11 and campus newspapers after tragedies. The clues they found were the use of past tense way beyond what’s normal. You talk about other people a lot. You use very negative vocabulary. And you use the first-person plural — you use ‘we’ or ‘us’ more often than would be expected.