I doubt the online ads thing can suck so much bandwidth...
BTW, it's not very nice to get to see that EULA after buying the game. But they will get away with it, you can bet.
Actually this hasn't been fully tested in the court system.
If you do not agree to that flyer, legally they would have to refund your money. A contract, by (abbreviated) legal definition is an offer
. Also, there has to be consideration
. Of course there are several other factors such as competency of both parties (i.e. you can't enter a contract while you are a minor or you are heavily intoxicated or you are under duress [someone is pointing a gun at your head]), the contract must not have illegal terms (i.e. murder for hire), etc...
Consideration means that one or both of the parties is receiving a measurable benefit or detriment (usually consideration = $ for at least one of the parties).
Consideration was given once you paid for the game (you gave them money and they gave you a game). However, because the entirety of the offer was unknown to you before acceptence, the consideration that you gave the other party is recoverable. This is known as a remedy (remedies are technically when one party does not live up to their obligation and has to assume a penalty). However, its arguable that the offer was known to people or organizations interested in the product (maybe they published the ad information on the internet) and you didn't bother to look it up. That is the grey area.
btw, IANAL (I am not a lawyer), however I got A's in all my BLAW (business law) classes and I am personal friends with several lawyers and lived with one while he was going through law school (& helped him study).
ninja edit: I just found a great Wikipedia article about basic contract law. I think that a bunch of business classes should be required by all people seeking bachelors degrees. No matter what you end up doing, it will always involve business somehow. http://en.wikipedia.org/wiki/Contract_law
edit 2: I hope all the readers understand that I am talking about the USA court system.