Doubtful, it's the beverage of choice in China and South-East Asia. Also, really full of antioxidants, more so than us Brits usual brand of tea.
If anything, the general consensus is that MORE people should drink green tea. In the company where I work we have several Chinese nationals who all swear by it. And they look healthy for it, but that might be due to the fact they don't get bladdered every weekend like the rest of us!
I drink around 4 to 5 cups of this a day and seems fine - I have done for a long time. Some brands have caffine in it and some don't so I suppose if you are drinking one with caffine you would not want to have too much - I don't the the amount of caffine compares to that of coffee though.