Quite a bit. Dr. Oz is a quack. He gets a lot of criticism from the scientifically literate crowd. He is terrible.
I drink at least a liter or two a day. Diet only.
This.
I drink a can or two a day of diet (Coke Zero). I rarely have regular soda. The exception being Sprite with a meal out every now and again.
The ignorance by people and fear-mongering perpetuated by the media on slow news days for Diet Soda is laughable, and without almost any scientific merit whatsoever.
About the WORST thing about Diet Soda is that it
may potentially in
some people inhibit ability to judge caloric intake, or trigger "sweet tooth" cravings. Meaning, of course, the soda itself does NOT make you "fat", but
may potentially in some people" make you want a donut more.

It's also acidic, which over a long period of time, can be tough on your tooth enamel if you consume large amounts daily.
Other than that, the science just isn't there, and it becomes a matter of "well...that sounds scary either way, I don't care what science says!" attitude that infects pop culture.