One use case that came immediately to my mind is virtual texturing (think megatextures like in id Tech 5) or virtual geometry (...which in current hardware can

One use case that came immediately to my mind is virtual texturing (think megatextures like in id Tech 5) or virtual geometry (...which in current hardware can be implemented via virtual texturing). The texture pages can take a TON of disk space so compressing those is important. But you can load (or mmap) the entirety of each page and you know beforehand how big each page will be in memory. (though all that assumes LZMA decompression is fast enough)