I've been going over this week's updates, and ran across this post in CodeBetter , that talks about why classes should be sealed by default, only to be unsealed by the 'unsealed' keyword. I couldn't disagree more. I think that you need a hell of a good reason to seal a class, so claiming that most classes should be sealed is a bit seems outrageous to me. I believe it's absurd to prevent extensibility for your classes, and if classes are sealed by default, the result will be...