Early on in my career I added comments to nearly every line of code, as you may do perhaps in an ASM program. As time went by I ran into many of the problems mentioned here. It was a bear to maintain which resulted in not updating comments and then they become stale at best, usually moldy.
I feel that the # of comments should reflect how complex or non-obvious the code itself is. In a more challenging environment, such as ASM, you will probably need more comments to understand what is going on. In more modern languages like C# you shouldn't need a whole lot of comments in most cases.
Generally I use tools that evaluate the complexity of my methods in C#. Those that are high on the complexity scale first get refactored. Then when I'm satisfied with the complexity remaining and I still have some code that is not obvious, or even more important, seems obvious but does something different, then I tack a comment on it.
