I won't buy it, if I had already bought a game that contained ads I would return it. If they refused to return it for a full refund of the price paid I would follow the chain of command.
If enough people say Average games with 100 milion lines of code (just a example) and a playtime for first round is 12 hours and averagely cost $65. Then this game of the same specifications will need to cost XX less to make up for the ad placements, if not, we need to have a CTJ meeting with the dev and some class action lawyers.
I agree with Mussels, I buy the game, then have to pay for a internet connection to download ads I will be forced to watch for X or XX number of seconds? There is a reason that you can skip or fast forward past the ads in movies, years ago when Betamax and VHS were new these same assholes tried to make them illegal, as you COULD fast forward past the ads. The supreme court ruled that was legal, and allowed under fair use. The same precedent applies (at least in the US) today. If you have PAID for something, you are legally allowed to skip past the parts of it you don't want.
This could also be likened to an ad in a magazine or book. You are not legally prevented from skipping them, tearing them out, or reading the last few pages and then the rest. You do not have the right to reproduce or sell copies you make, but you may make the changes you desire, with the only recourse is the originator does not have to support or warranty said product.