I love Venice and believe that there should be some restrictions imposed to change the "limits" of the number of ships/day allowed. It has become popular for a reason and if the cruise ships and tourists leave it will not "help" Venice it will hurt it.
The northeastern part of Italy is doing much better than the rest of the country because of it's manufacturing, textile and tourism industries. If you take away the tourism portion then northeastern Italy will go the way of the rest of the country.
I do believe that tourism and cruise passengers need to be controlled but not so tight it strangles the city.