Why did the Yes side win?
I attended several of the No campaign's meetings, visited their websites, read their booklets etc.
Based on my personal experience, I think what went wrong could be summarized in one sentence: If you want to win a referendum, you have to appeal to a majority of the voters. That is, you have to be able to appeal not only to the pot-smoking leftists (most of whom I imagine still live in their parents basements and claim to have been abducted by aliens).
The No campaign was directed entirely at the left-winged voters, ie those who were already against the treaty. If you want to win a referendum, you need to step out of your comfort zone and pursue the voters who doesn't think like you. If you're a right-winger trying to win a referendum, you have to find arguments that appeal to the left as well.
Instead, the No campaign wasn't so much a campaign against the treaty, as a campaign against capitalism itself. And, surprise, most Irish people even today don't support a planned economy.
I read a booklet published by the No campaign, where instead of pointing out the loss of independence that comes with the treaty, the author went to great lengths in criticizing Friedrich Hayek and Milton Friedman - both of whom are dead today, and neither of whom supported the EU project in the first place. Talk about a waste of time! And even if Hayek and Friedman had been alive (and had supported the treaty), what's the point in talking about them?
The No side deserved to lose. They could have talked about the loss of independence, the unnecessarity in bringing government debt down to a level as low as 60 % of GDP (many countries -including Germany - have higher debt and are doing just fine), the fact that the bailout fund that Ireland is going to have access to may not become a reality (or may not be as big as is claimed)... there were so many arguments, why only use the arguments that only appeal to hippies?
Libertas was a breath of fresh air, but it came too late.
What do you think was the reason the No side lost?