With the globalisation that's going on for the last couple of decades and the fuckups of the EU (which seems to be run by idiots if you ask me), I can understand the desire of some people to govern themselves locally. And if they want to do it, it should be their right.

Hey, I think getting the UP in exchange for Toledo was the best deal evar. Love you guys. (I almost went to Michigan Tech.)

Quick notice from an italian law student (I hope something similar has not already been posted): a Venetian independence referendum is illegal, based on the article 5 of the Italian Costitution. To be more precise, the voice "una e indivisibile", translated "one and inseparable" prevent any attempt of secession (which, by the way, could even be marked as one of the most harshly punished crimes if seriously pursued). So, no matter the results, the referendum will have the same impact of a joke.

Exactly this^

But useful for establishing a perimeter that no one will approach.

Think its likely agaisnt the terms of the Geneva convention, possibly a biological / chemical war crime as well.

Constitution get revised sometimes... Though of course 'the many' will never agree that the few who support them to leave them.

Sooo, what would italian goverment do in hypotherical situation where most venetians would vote for independence and start the process of seceding? Throw every venetian in jail? Have military occupy venice?

They just won't do it. Actions like these have the exact nature of adolescent riots; as I said there's no *real*, deep reason to do it, as soon as they notice the sacrifices they should do to really secede, they will take all back.
Else, I guess they could be prosecuted for acting again the constitution.

I can't give you a real answer, because something like this never happened, and probably never will. The only real case of attempted secession was when some decades ago a very small group of separatists tried to seize control of Alto Adige to annex it to Austria, but they used very violent means: official reports said that there have been nearly 150 terrorist attacks in just one month, varying from electric centrals sabotages to murder. Since the vast majority of the population was not involved in this, it has been repressed by ordianry means and all the responsables have been prosecuted and convicted. Well organized, I must admit, but definitely not expression of popular agreement.
Back to your hypotetical situation... there are at least two motives why I think we'll never see a secession: first, because unlike what someone seems to think, almost no one wants to secede. Everybody knows that they (a generic "they", I'm not talking specifically about Venice) wouldn't last much without the rest of the country, interdipendence between territories is just too strong. Second, because Italy is divided in regions, and all of them already have a very large margin of autonomy, not unlike federal states: if they want more, they just need to legally ask, and once again EVERYBODY knows that.
Lega Nord has already been mentioned: since their foundation, there's a new referendum for secession every couple of months... everyone in Italy knows that this kind of initiative has not to be taken seriously.

Something like IRA of north ireland or other such separatist terrorist organisations that take up arms when population at large does not care about their agenda?

If there is already legal way to gain more autonomy, I see even less reason for them to secede. If they have problem with something governed by central goverment, just push to have right to handle it yourself and see if you can actually do it better.

And now a little bit of comic relief....topic related of course!

I think you misunderstood both the situations, but it's fairly normal for a foreigner not accustomed to our daily madness. I'm sure that if you lived here you would have my same thoughts... let me explain better: the South Tyrolean Liberation Committee was not even remotely similar to IRA. They were a small terrorist group driven more by their fanatism than by common believes of the population. This is demonstrated by the fact that they didn't survive very long after the "night of fire" (see google for this, it wold be too long to explain). Why? Because they never had their own people's support, and more so when they started to use bombs in public places. Not a great way to win trust and support, isn't it? People keeped on fighting the legal way, and now they have the widest autonomy of all the regions, nearly a "state in the state". The Italian government never tried to repress them, so they never had reason to take up arms. This was never like northern Ireland!
Don't be fooled by what you read: those so-called "separatists" are nothing more than a couple of hundreds of xenophobists in a city of more than 270,000 inhabitants. Venetians do not want independence. I'll repeat myself: there is an unofficial referendum about secession once in a month, but any time the votes hardly reach 1000 units. They are nothing more than a farse.

Anyone know when the results are in?