The proponents of the Lisbon treaty will claim that it's unfair for Irish, less than 1% of EU's population, to prevent the treaty from coming into force. But, as pointed out by Dave Kopel,
The very fact that only 1% of the EU's population was allowed to vote on a treaty [...] was itself an illustration of the enormous "democratic deficit" of the EU in general, and the Lisbon Treaty in particular.There could be more countries rejecting the Lisbon treaty in referendums, if there were any other countries holding referendums on it. What can one think about the EU leadership which had one treaty ("EU constitution") rejected in referendums and then decided to avoid that by simply not holding referendums on the next one? They fully deserved what they got in Ireland this week.
The pro-Lisbon side will also complain that the existing EU treaties don't allow to expand the union to more than 27 countries. Technically, it's accurate. But it's easy to write a 1-to-2 page document amending the clause that limits EU to 27 countries and a few more related clauses. What EU leadership did is, they tried to package 398 pages of other stuff and slip it past the voters, using "we can't expand EU to more than 27 countries" as an excuse. Again, they deserved what they got.