In reply to the "it doesn't affect sovereignity" argument which has being used on this topic, under international law the only way to get out of an international treaty is with another one. In other words, at this current time, even if a member state wanted to leave the EU, unless the EU let them leave, they would be trapped inside, just like Hungary was trapped inside the Warsaw Pact in 1956. - so yeah, combine that with the fact that EU law is supreme to national law and it does affect sovereignity. The Lisbon treaty includes a withdrawal mechanism though - article 50, under my interpetation, means that unless the member state and the European council agree together to extend the period, if a request to leave is sent in then it's possible to withdraw 2 years later. Anyway there will probably be more votes till the answer is "yes", just like with the treaty of Nice. The referendum is pointless anyway because of the disinformation from both sides of the campaign meaning people don't know what they are voting for, although a lot of the politicians probably don't know either.