Has it been scientifically proved that Coca-Cola ...

Not really. Coke is no more dangerous than any sweetened carbonated soda, whether you factor in the sugar or the artificial sweeteners.

There has been talk of rust and blood cleaning etc, which may even work, but the mythbusters proved in one of their shows that teeth do not rot when soaked in coke for the night, and we have to remeber the human body is not a sterile or neutral environment.

Yes, water would be better, but that's true anyway...

This is the Mythbusters link (on the Discovery Cahnnel). Maybe you can see or read some about their experiments. 

Nothing scientific but worth watching:

I think it's important to remember that whenever you see studies done about something specific being bad for you, take cola or sweet and low as examples... scientists do experiments on how a ton of this product can eventually have it's effect on the human body.  So yes, it has been proven the if you drink a lot of coke, coke every day, for example, that you may very well have problems with your teeth and gain weight from all the sugar.  However, if you have a can of coke once or twice a week, this isn't going to kill you, or really have an effect at all.  The point is, is that everything should be done in moderation.  Coke can become addictive and you should be careful from that.  I personally made a rule for myself that I'll only have some Coke on the weekends, not during the week.  That means that I'm creating an easy method to moderate my intake of Coke.