Is it becoming trendy to disregard the Constitution?

I’ll admit that I don’t pay enough attention to politics or government, but it seems difficult to miss the fact that Bush & Obama have both taken big jabs at the Constitution.
Can you give me some examples of ways that this has happened with past presidencies?
Should we be concerned about this happening with future presidencies?
Were you surprised by the contents of the National Defense Authorization Act? Were you surprised to see it come from Obama?

Any thoughts on the subject are welcome, but I am really most curious about the possibility of this becoming a trend. I try not to run leaping into conspiracy theories, but I can not be the only person that feels like something fishy is going on.