This article is from the Foo Fighters FAQ, by Ben Rogersbenson@unix3.netaxs.com with numerous contributions by others.
Well, you didn't read this FAQ to find out where to find
Seriously though, the issue boils down to this: you are
obtaining a digital copy of a song that you did not purchase,
which in turn means that you are not compensating the artist who
created the song. This is especially problematic when you are
asking for a song that is available on one of the Foo's major
releases, such as "Everlong" or "Big Me." Not only are you
asking for something that's readily available in music
stores, but the CDs are also now available from such places
as cdnow.com (which, coincidentally, also has samples
from the songs on the albums) on the net. This tends to raise
the ire of some of the regulars of the newsgroup, and thus
the rather negative responses to your post.
If you are really desperate for the mp3s, and are possibly
just looking for rare releases that you can't find in stores
(such as live performances), your best bet is to use one
of the many, many mp3 search engines available on the web.
A fairly decent list of available mp3 search engines can be