h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

From my experience, Vespas follow their own set of rules in Italy. In Florence, which sufferes from a massive Vespa infestation, these motor-scooters travel in packs of 2 or 3 down narrow cobble stone streets at top speed. Pedestrians beware: it would be foolish not to hug the side of a building if you hear a Vespa coming in your general direction. Even if they have 4 or 5 feet of roadway, they will inevitably almost hit you on the sidewalk.

I must agree with your assessment of the Vespas in Florence. I was there in May, staying in a small B&B on the Arno, where I was awakened every morning to the thundering hords of polluting beasts. Reminded me of the time I was in Tokyo walking into the train station only to be greeted by about a gazillion salarymen (and women) coming out. At least in Tokyo they weren't going fast and belching smoke (I think).