In a big project I work for, I am considering recommending other programmers to always seal their classes if they haven't considered how their classes should be subclassed. Often times, less-experienced programmers never consider this.
I find it odd that in Java and C# classes are non-sealed / non-final by default. I think making classes sealed greatly improves readability of the code.
Notice that this is in-house code that we can always change should the rare case occur that we need to subclass.
What are your experiences? I meet quite some resistance to this idea. Are people that lazy they could not be bothered to type sealed?