Some things spread out on a makeshift table, on a sheet, or directly on the ground. Roving (usually) fellows pushing bracelets, umbrellas and whatnots at you. You've seen it. You might even have been tempted to buy something from one of them.
That faux name brand bag or pair of sunglasses does look so convincing, it's so lovely, and it costs a fraction of the original. Maybe it is real (if so, it's probably stolen). It suddently has started to rain cats and dogs....More...
Do NOT give in to temptation!
First of all, you're risking an enormous fine, beginning at Euro 1,000.00!
Look what the U.S. government page on travel to Italy has to say:
"According to Italian Law (Law 80 of May 14, 2005), anyone caught buying counterfeit goods (for example, DVDs, CDs, watches, purses, bags, belts, sunglasses, etc.) is subject to a fine of no less than EUR 1,000. Police in major Italian cities enforce this law to varying degrees. You are advised to purchase products only from stores and other licensed retailers to avoid unknowingly buying counterfeit and illegal merchandise."
Second of all, you're feeding the various mafias and crime.
Third of all, those vendors do not pay taxes (which means us honest folks have to pay more taxes to compensate for your ill-advised action), and the products have not passed safety tests, and may even be harmful (sunglasses probably don't have the UV filter necessary for protecting your eyes, and things for children are probably toxic, flammable and have lots of dangerous detachable pieces).