I dread the day have to moving house. At this point we have four big and two small bookcases and about 650 books. Which is not a lot, actually. But when you have to move, it is. I cannot imagine the hassle to put all the books in boxes, which cannot be too heavy otherwise you cannot carry them. After that, I have to take the bookcases apart. Since they are from IKEA, this is an extra stressful idea.
It does not have to be, if you use folding bookcases. I did not knew they existed, but apparently they do. They are not as pretty as mine, but if they are filled up who will notice? You can find them here.