The US,at least, no longer allows extra pages, I just had to change to a new passport because of this. As it happens my first trip with the new passport was to Ireland and since I flew through the U.K. I got not only the huge Irish stamp I also got the U.K. Stamp for the privelage of transferring at Heathrow. This combined with the Chinese and Vietnam visas will mean a new passport every 2 years now. I know it's not a big issue in the entire scheme of things, but changing a passport is a hassle.