When I changed host last weekend I imported my blog and used the WordPress import plugin. I was very amazed that this resulted in a disk space used of over 300 MB (previously only 12 MB and the xml-file that I imported has a size 1.11 MB). When I checked where this disk space use comes from I found that this was caused by the number of images in the wp-content\upload folder. Most of my images now exist on the server in 25 different resolutions. All of these images were created in the few minutes during the import.