Hrm, the day one DLC only worries me if the actual game is adversely affected. My only question is if the retail game is worth the price you have to pay for it. If it is, I'll buy it. If it isn't, I'll wait for a price reduction. I then separately evaluate DLC to see if that content is worth the price I'd have to pay for it. Sure the game would be a better value with the DLC, the question is if it is enough of a value without it.
From a publishers perspective, day 1 DLC is the best DLC option. It is when the most people are interested in the game and the most likely to purchase new content. An enterprising publisher may start trimming stuff out of the original release to make DLC, but they walk a fine line here. Trim too much and initial sales decline, which then declines the market for your DLC. Of course the fun thing about capitalism is that cutoff point for this is different for everybody. Seems like even the offer of DLC on day one is the cutoff for some, but not for the majority of people.
I do not really see how day 1 DLC will adversely affect CIV. The only way I could see this happening is if there are only 8 civs and greatly trimmed research/unit trees...and the game stops in the industrial revolution and to go further you have to purchase the "modern era" DLC. Seeing the plethora of DLC and pre-order specials that are more than just a vanity item, I will certainly keep an eye out on reviews etc for info on exactly what is included in the basic retail game. Thing is that CIV provides hours, days, OMG IT'S FIVE IN THE MORNING, type of entertainment that is an absolutely amazing value at $50. They would really have to fuck things up for me to not find value in purchasing at launch.