I found out that a girl I was seeing last year had glandular fever and didn't tell me.
I also know what a vaginal prolapse looks like, B-movie horror flicks use dry ice and virkon to produce that bubbly cauldron look, chinchillas will eat meat and old people are an unbelievable burden on the country's finances, especially where healthcare is concerned, but also in many, many more ways.
Also, no matter how high up someone is in medicine or management, if you know what you're talking about you can really make them look stupid. They hate it when their position doesn't carry as much weight as they think it should.