Usually preformatted is used by programmers to show and discuss sourcecode. The above example shows how non technical users might use this element for 

!Guitar Chords

see [http://commons.wikimedia.org/wiki/Category:Chords_in_guitar]
{{{
C

||---|---|---|
||-0-|---|---|
||---|-0-|---|
||---|---|-0-|
||---|---|---|
}}}