Saw an interesting comment in an interview with Greg Zeschuk that he was giving about ME2 that pertains to the DLC debate:
Originally Posted by Greg Zeschuk
[...] it is interesting dealing with Microsoft and DLC, because the DLC has to be self-contained. You can still do a story, like over three chapters or something, but you would need to build it in a way that you are able to play the second one independently and not have to purchase the first one
That's an interesting point, and potentially explains one reason why DLC is generally so lame. I would assume Sony has it own rules pertaining to DLC as well. Seeing as DLC has to be standardised across all platforms (lest one group complain they are missing out) and meet all platform restrictions, it's no wonder it is mostly throw-away filler.