Regarding the Microsoft built classes that inherit IDisposable, do I explicitly have to call Dispose to prevent memory leaks?

I understand that it is best practice to call Dispose (or better yet use a using block), however when programming, typically I don't always immediately realise that a class inherits from IDisposable.

I also understand that Microsoft implementation of IDisposable is a bit borked, which is why they created the article http://msdn.microsoft.com/en-us/library/ms244737%28v=vs.80%29.aspx explaining the correct usage of IDisposable.

Long story short, in which instances is it okay to forget to call Dispose?

Regarding the Microsoft built classes that inherit IDisposable, do I explicitly have to call Dispose to prevent memory leaks?

I understand that it is best practice to call Dispose (or better yet use a using block), however when programming, typically I don't always immediately realise that a class inherits from IDisposable.

I also understand that Microsoft implementation of IDisposable is a bit borked, which is why they created the article explaining the correct usage of IDisposable.

Long story short, in which instances is it okay to forget to call Dispose?