Have you ever examined a hard back book? Are the pages individual and stuck to the spine? Look carefully at the top (or bottom) of the spine and you will see that the book is made up in sections. Take 2 pieces of paper - same size - place together and fold in half and number the pages 1-8 - top centre. Flip through and you will see 1, 2, 3 ......8. Take out the centre piece and on one side you will see pages 4 & 5, what's on the other one? 1 & 8 and 2 & 7. Write 'A' on page 1, 'B' on page 2 .....'G' on 7 and page 8 leave blank. If you have a long arm stapler, staple the pages together - if not - tie a piece of cotton across the fold. You should now have an 8 page 'book' with letters A to G on 7 pages and a blank page. Now we don't need a blank page, do we? OK, rip it out. Ooops, not only have you taken page 8 out, you've taken page 7 out as well and your book has fallen apart but we already knew this and what has this got to do with 'This Page Intentionally Left Blank'? Andy mentioned NATO docs - think of a 2 page chart, do you want me to print half if it on page 33 and the other half on 34 or would you like to look at the whole chart on 34 & 35? That chart marks the end of section one of the manual, now what do you want me to do next - start section 2 on page 33 or page 36? "Well, Hippo, the chart is part of section 1 so we will start '2' on 36 but then someone make think that page 33 has not been printed." "OK, I'll print on 33 'This Page Intentionally Left Blank' and that will keep everyone happy! "Why does this happen on some computer generated docs? Blame Bill Gates and MS Publisher - if you have the printed version of a document, there may be an empty page on it and it will be the same on the computer version.
Do you remember when MacDonald's, I think, starting printing 'Caution Hot' on coffee cups to stop people suing them. Another reason for 'This Page Intentionally Left Blank' is to stop people going back to the book shop and whinging "There's an empty page!"