I use YYYY-MM-DD in my computer, because then it knows how to sort them (i.e., when I copy pictures from my camera, I put them in directories like 2012-01-24, or 2012-11-06, and then they get listed in the correct order). This also allows easier manipulation with calculations in scripts, etc.
However, when dealing with people with different regional backgrounds, etc. then a textual month is preferred (less ambiguity), so 2012-Jan-24 (or any other arrangement, such as Jan. 24, 2012).
$0.05 (getting ready for when Canada turfs the penny).