I've had many a documentary ruined by background music, most notable any of the David Attenborough ones, where his soft-spoken words get drowned out, and there's many doc. where I have given up with it or used the subtitles if I really interested.
BUT FFS, there are some superbly ridiculous situations where background music adds nothing, so why the f**k do they do it?
Take the BBC Final Score prog. at tea-time on BBC1, when at the end they give the results, and while they are showing/explaining the ups and downs of the tables, there's music playing in the background. WHY?!?!?!?!?!?