Baseless rumor. The DLC activates and then you always have it even when offline.

But you still will need internet at first in order to activate and download DLC's.

Actually, I believe Phoenix may be right. I was playing the other day and my internet connection went down entirely, which meant I couldn't log in to the Dragon Age servers. When I tried to load my saved games, I got messages saying that since my saved games were made with DLC that I wasn't "authorized" to use, I wasn't allowed to load them.
My copy isn't retail, though. I bought off Impulse.

Yikes! If it's true for retail boxes as well, scratch that game off the list, then... I have an external modem at home and for added security I only turn it on when I actually want to be online for some reason. Online for a single-player game? I think not.

Hmm. I just tried to disconnect internet and play the game. Savegame loaded and I travelled to Warden's Keep zone just fine. Steam version.

I got the same error when loading a save file before it logged into DA:O's servers, I quit the save game and entered back in, and it was fine because I logged in. I wasn't without internet.
I also have the Impulse copy.

Not a baseless rumor.
I have the game (bought via impulse, DDE edition) and if my net goes down and I try to play with a save that has all the DLC on it, it willt ell me I need to log in to that account in order to play.

Was the game still recognizing you as logged in with your proper account information?
Let me clarify. My connection cut out as I was playing the game. I noticed a few messages as I went along saying that the game couldn't connect to the Dragon Age servers, but just ignored them and kept going. I eventually stopped playing, quit out of the program, walked away for a few minutes, then came back and started it up again.
This time, when I started it up, the game couldn't log me in automatically because it said I wasn't connected to the internet. I went to check my cable modem. Service was down. Looking on the bottom left corner of the screen, at the main menu, where it normally has your account name? It said "Logged Off." Trying to load saved games from that point did not work.
Apparently, if you still have an active log-in, even if your connection goes to hell, you're ok. Otherwise? Boned.

No, I disconnected the internet, then I had to restart Steam in offline mode, then I launched the game. The game was showing me "Logged off" in the left bottom corner. And still I was able to play.

Same here. I was logged off in game and yet all my DLC was accessable. I was using the Retail version though. AFAIK and As far as Bioware have said the DLC only needs to be activated online, from them on you should always be able to access it offline. If you are having trouble I would suggest contacting them.

Well, let's see. So far, we've got three people who can't use their DLC if their net connections go down. And all three of those bought the game on Impulse. It just seems that Stardock sold us a lemon or something. First, that problem with not installing the service to even properly download/install the DLC in the first place and now this?
Yeesh.

Btw there's option RequiresAuthorization="1" in My Documents\BioWare\Dragon Age\Settings\AddIns.xml for each DLC. It might help to change it to RequiresAuthorization="0". I didn't do it though.

Almost baseless... what happened was there was a bug in that a certain file wasn't getting edited properly (addons.xml or something like that) usually do to Vista/Win7 UAC. If you just opened that file and changed the Auth=0 to a 1 (or something like that I don't have the details in front of me) it no longer needed to authorize online every time.

Sielle's right. This is, in fact, occurring, but it's not intended. From what I understand, they're working on getting this fixed, as the intention is you only have to authenticate the DLC one time and thereafter you don't have to be connected to the internet.

Thanks to everyone who commented for bringing a bit more clarification to this matter.