Are tourists ruining Venice?

In front of me, a sea of people spans in all directions, even as the gray clouds above us threaten to burst. Deep in the heart of San Marco Square, and what I deem the heart of the touristic center of the main island which makes up the step-back-in-time Venice, the tourists are unavoidable. In fact, here they are more in my face than any other place I have visited (and I am counting the mass of people gaping at Mona Lisa at the Louvre).