This is exactly what I did for a research project in school: download Wikipedia, extract all combinations of iirc 2-5 words, do a few transformations like addin

This is exactly what I did for a research project in school: download Wikipedia, extract all combinations of iirc 2-5 words, do a few transformations like adding a lowercase variant and space-less variant, and run that set against the LinkedIn sha1 password dump. Quite effective for cracking passphrases that weren't randomly chosen words but an existing phrase.