Two groups have always understood the principle that you can only have one government per currency.
The Synarchist faction of the european political class have always sought to forge a non-democratic oilgarchical United Synarchy of Europe for their own advantage, and they have used the single currency to try and force political union in through the back door whilst pretending otherwise.
Euroskeptics have of course understood this as well, and they have fought an uphill battle to expose the Synarchist agenda which devolves from the thinking of Yves saint D'Alveydre who wanted government by a shadowy unelected cabal of 'people who know best' that controlled all aspects of the life of the populace. (see Wizards Against Tyranny paper on this site)
The european union does not exist for the benefit of the european people, it exists for the benefit of a section of the european political class that would prefer to enjoy the delights of self-perpetuating arbitary power without the occasional inconvenience of facing an electorate.
The current financial crisis has come a little too early for comfort for the Synarchists, it has become all too apparent that any nation which trades its political freedom for financial gain will end up loosing both. Neither Greece nor Italy now has a properly elected government, each now has a junta of EU approved eurocrats in charge and years of political slavery and austerity ahead unless they have the guts to default.
The British have for centuries understood that the strength of europe lay in its diversity and for centuries British foreign policy has centered on denying anyone hegemony on the continent, not Phillip of Spain, not Napoleon, not Hitler, and now not Merkozy in cahoots with all those unelected Euro-Mandarins whose names and faces and roles hardly anyone knows.
Finally after some decades of appeasement we (apart from a few illiberal dimocrats) have finally had the guts to say no. This will hurt for a while as the whole corrupt rotten synarchist edifice of the EU crumbles, but a few points off gross domestic product for a while seems a small price to pay for the freedom to run our own country. We probably won't now have to trudge wearily down to Dover with our longbows or muskets yet again, thank goodness.