In Venice you will find beautiful historic sites that are more than fantastic! But you will also find increadable crowds so much so that you feel like you are in Disneyland and not Italy.
But the most dissapointing thing you will find is that some eating establishments will charge outlandish prices for drinks. A La Bricola is just off San Marco Piazza at San Marco 475-6. Its a medium to low prices rest with not very memorable food. THey charge 7 euros for a coke and then same for water and 12 euros for a glass of house wine or beer. So for two people you can easily double your bill without knowing it.
I realise that this is a tourist town but when locals take advantage of travelers like this you cant help thinking that one visit is enough.
I speak Italian and work for an Italian company and when I relay this to natives who live in the region they all say in Italian what is the equivalent to "big ripoff" and "that's why I never eat there" or "its only for tourists stay away".
Italy is beautiful and the people are in general wonderful so dont let these type of ripoffs stop you from going and enjoying this magical place!