Game sales always drop substantially the second week. Anyone who really really wants it RIGHT NOW will buy it day one, if not week one. This doesn't mean anything.
Also, in regards to 'It's sales are dropping faster than the DA:O sales did' remark.
Sure. So did ME2's sales drop faster than ME's sales. For simplicity's sake, let's just look at one platform, the XBox 360.
Week 1, Mass Effect sold 258 thousand copies, with a 23% drop in the second week. Conversely, Mass Effect 2 sold 668 thousand copies week 1, with a 75% drop in the second week. OMG! THAT'S HUGE! CLEARLY ME2 IS A FAILURE! Wait, no, it actually has ended up selling almost exactly as much as ME1 on the XBox 360, despite the fact that ME1 was out longer.
I'm going to make baseless hypothesis for why this is:
When companies invent and start experimenting with a new license, there's no recognition. No one can look at Dragon Age or Mass Effect and go "Oh, I played the last one. It was really good. I'll buy this one too." Instead, what Bioware is trading on is the publicity it's managed to generate for the game itself, and the weight of its own good name. The result is, that the experimental gamers, or those who follow gaming media, may be the majority of gamers who buy that new property in week one. But then week two comes around, and what happens? Sales remain pretty strong, because now everyone's hearing the reviews, they're playing it at their friend's place, and they discover, hey, that's a pretty good game.
Conversely, when ME2 or DA2 roll around, people already PLAYED the first game. Suddenly, Bioware is dealing with something much more powerful to the gaming audience than whether or not they like bioware games. They're dealing with whether or not they liked the first game. It doesn't matter whether I'm an experimental gamer. It doesn't matter whether I follow gaming media. I played the first one. I liked it. I trust that this game will be good as well. So week 1 sales get way higher, but sales in week 2 and beyond have a smaller portion of the potential 'wait and see' audience.
This has been my long winded and baseless hypothesisisisis session. I hope you don't want your 2 minutes back. ._.