as you might know, PS3 is region free.
for games that is.
you still require the correct version of DLC for it to be able to work with your game.

but i still don't get the region locking thing.
is it locked like Region 1,2,3,4?
or is it locked like PAL and NTSC?
if the 2nd is true, then would a US DLC work with Asia version?
just need a confirmation, because i have a pretty solid evidence... (oh smokes, too much Ace Attorney) that it does work, because my Region 3 disgaea works with the DLCs Azumi purchased (which is from the US store)
but my Disgaea also have trophies and such, which is said to be US version only (shrug, you tell me).

I'm a bit confuzzled myself. anyone care to elaborate it for me?

PAL and NTSC... unless I'm mistaken.

The US version should work unless it had some changes (which are reflected in-game).