Something about either Alliance, Minor Illusion, or how brownies react to the combination of those two spells does not seem to be mimicking live. According to the comments at the 1999 archived copy of castersrealm, Erudites start dubious to brownies, do not notice a faction change (still dubious) with Alliance, but are raised high enough by minor illusion to purchase spells (probably apprehensive -- this isn't discussed). Sorry I don't have an example that isn't also possibly a failing of another spell but this is the only time I've had reason to use it so far.
See comments at:
http://web.archive.org/web/200101080...sp?SpellID=171