Textual dumps of SQL databases also fall in this category. I remember having downloaded a huge sql dump. I couldn't open it in most editors because they all buffered into RAM. The file was about 13G in size and did not fit into the RAM of any machine I own. But in this case using ropes wouldn't have helped either, I guess.

Text editors should also take huge files into account and provide sequential reading from the disk to memory. Even on Emacs, I couldn't work with the file. I ended up fixing it and importing it to Postgresql. And then I spent hours on indexing the necessary fields :).