I noticed that when Light Yagami got the Death Note he became evil, so it made me wonder if the Death Note has the ability to corrupt a human user.
"Power corrupts; absolute power corrupts absolutely."
It appears that the Death Note does not change the owner's will to corrupt him directly. Light, though, is corrupted by his rather insane ploy for power and world domination. While he almost immediately exhibits megalomania, he seems to try to morally justify his actions. By the end, he views himself as a God and cannot fathom his failure or that his actions are somehow wrong. Misa Misa, however, seems detached from those under her feet and doesn't seem to give much mind to whether her actions are moral at all. It seems that the Shinigami's expect this kind of behavior from human's given this power but they are too surprised by it to be directly bringing it about.