Venice has only approximately 55,000 full time residents. 20 million people visit Venice annually. 20 million. Many people only visit on day trips as the harbor can accommodate all but the most behemoth of cruise ships. In many ways, Venice is one of the greatest tourist traps in the world.
Despite the hellish masses of people during the day and boat traffic on the main canals, there's a certain quiet due to the absolute lack of cars; its nickname is, after all, La Serenissima. Part of this city's charm is getting lost in the labyrinth of bridges, piazzas and streets and finding your way back to your hotel. It is also almost magically beautiful. Normal life in Venice looks like artwork. The light is clear and crisp and shimmers off the water almost everywhere. People dressed up for Carnival do not seem out of place at all. Spend a day or two there and you somehow don't mind paying a premium for mediocre food served by surly waiters that don't really want you there.
On one visit I decided to walk across the city at night and photograph it. What surprised me most was just how silent the city was at 3:00 in the morning. From the Arsenale to the train station, I met only two other people: one security guard in front of a hotel and one very drunk tourist trying to get into his hotel. Piazzas dressed up for parties were deserted and a giant pair of lips hovering mid-air welcomed me to the end of my walk.