It is not statesmanship but it is clever politics. I think this will put Labour in a difficult place for the next election.
The real trouble is that it is too easy to knock the EU, because it is dysfunctional in so many ways and does need radical reform (wasteful Common Agriculture Policy, the shameful ongoing failure to have audited accounts, the 2 separate parliamentary sites etc). Pro-Europeans need to face up to this.
So it needs desperately to reform but if the UK does leave, is this a cut to your nose to spite all our faces?
Cameron should be in a strong position to get his way within the EU since the Euro countries also need drastic political change to save their currency and UK could make things difficult (or rather make things even more difficult) unless they play ball.
So this is not a good day for Europe or democracy.
The public can vote on Europe in 2015, at the next British General Election. Let the batty UKIP stand on its own merits and and see if they win a majority of MPs mandated to leave. That should be our way of deciding such things.