I've come upon a really authentic site about Venice called Venessia.com. It's almost entirely in Italian, unfortunately. But what really got me was a page that was a little compendium from their Venetian readers about encounters of the worst kind with tourists, including other Italians.
Here are some of my favorites:
Italian lady asks Venetian: do you always speak Spanish here or do you also know Italian? (Venetian dialect sounds a lot like Spanish)
Various tourists: where is St. Peter's?
Foreign lady: where is the Ponte Vecchio? Venetian answer: in Florence.
Tourist from Ohio looking at city map: Excuse me, I can't find the airport on this.
American tourist: The city is great, but why did you build it near all those factories I saw coming in from the mainland?
Tourist from Florence: I don't want to be like everybody else and take a gondola ride. Do you have horse-drawn carriage tours?
Italian father lecturing wife and kids: "Because the King of Venice..." (Venice had a Doge, and was the longest-lasting republic in history)
Germans: Do you have electricity and running water?
American couple: Why do you have so many lion statues here?
My favorite: American lady asks how to get to Bye Bye One. Venetian thinks it must be a disco or eatery he doesn't know about, asks another Venetian. He gives lady directions to the seaside resort of Bibione (bee-bee-OWN-eh), which she pronounced phonetically in English. First Venetian asks second, astonished: how did you know that's what she was saying? Second Venetian: you don't think she's the first, do you?
(In the picture above, painting by Pietro Longhi of social gathering of Venetians, probably making fun of outsiders)