Yep, definitely underestimated the demand, Brad.
I think there's been a HUGE word of mouth spread over the past month. I'm sure many people who bought MOO3 saw the little flyer and were intrigued...then there was an ad in the latest PC Gamer.
But really, I think a huge amount of notice has come from disgruntled MOO3 people who saw various people talking about GalCiv on their forums. I know that's how I found out about it and I've seen numerous people saying the same thing on the forums here. For my part, I was just looking for a good new 4X space strategy game. I had thought for certain it would be MOO3. When MOO3 turned out to not be something I had fun playing, I looked for alternatives and found GalCiv.
So far I'm having a great time with the game, especially now that CariElf helped me figure out how to get the MP3 player working. I have to say, though, that I'm glad stores ended up getting the game in on Tuesday. Since that happened, I just went ahead out to EB and picked up a copy (and got my nice little book and quickstart guide and all). But before that discovery, when I thought the game wouldn't be in stores until Wednesday (today), I was planning on downloading the game at midnight the night before just so I could start playing it early and wouldn't have to deal with the hassle of driving out to the mall. I'll bet a LOT of people tried that, not because they couldn't find the game locally, ever, but because they wanted to have it and start playing it as soon as humanly possible. When game anticipation is high, even getting a game 12-24 hours sooner can be a "necessity" for the salivating gamer.
So, you undoubtedly got inundated by people who didn't want to wait for local availability and just jumped at the download option.
Hope that makes sense and maybe explains some of it for you.
~SDC~