Any ideas, in which cases a sealed class would make sense?

Answer 1

For example, a class Dog may be sealed so the class Animal won't be able to inherite from it (so Animal:Dog will create an error) but the opposite (Dog:Animal) will be possible

Answer 2

this stackexchange post collects many opinions on that same question http://programmers.stackexchange.com/questions/210461/how-can-designing-for-inheritance-cause-extra-cost