This is baloney, I'm afraid to say, anything granted to you under law is a right, whether it appears in the constitution or not, unless it flat-out contradicts the constitution. If you honestly believe what you've just written here, I'd have to advise you never to represent yourself if you ever find yourself before a beak.
I think we're dealing with one of those regional differences (not to mention semantic differences) in the concept of a "right." I'm a lawyer in the U.S., so when I talk about "rights", I'm talking about constitutionally guaranteed "rights" as in "The Bill of Rights." Your First Amendment right to free speech, freedom of religion, freedom of the press, etc. Your Fourth Amendment right to be free from unwarranted search and seizure. Your Second Amendment right to bear arms. Or arm bears. Which would be WAY more entertaining, in my opinion. But I digress.
Anyway, the U.S. enumerates certain specific "rights" which, while they can be abridged or waived or whathaveyou, are generally given a lot of deference in the law. You have to jump MUCH higher hurdles to beat a "but it's my RIGHT!" argument when you're dealing with these kinds of rights under U.S. law.
A EULAs "rights" are more "little 'r' rights." You have certain rights under the contract itself, in the sense that the other party has this or that obligation in exchange for your performance of a given duty (or agreement not to act, etc.).
Again, this is all under U.S. contract law and copyright law. Unlike the U.S. Constitution, the 1976 Copyright Act does not grant the consumer any "rights." Instead, certain portions of it LIMIT the rights of the copyright holder (such as the first-sale portion). All that the text of the Copyright Act stands for is that you cannot be sued for copyright infringement for selling "your" copy of the work in question. If someone says "You infringed!" you respond "Like hell. First sale doctrine, buddy." Infringement, however, is NOT the same as the EULA. The EULA is a private contract agreed to by two parties. It enumerates what the licensor chooses to give the consumer, and what the consumer may and may not do with the license. The consumer may choose to accept the terms of that agreement, or reject them and forego the use of the software.
Now, the enforceability of EULAs in U.S. law is tricky, and does sometimes run into problems re: copyright law. But I think it'd be a mistake to assume that a court would refuse to enforce a EULA's contractual prohibition on resales. On the other hand, if the licensor sued you for copyright infringement, you're safe. Two different legal claims, though. One is breach of contract. The other is copyright infringement.
We worry about piracy. I'm wondering now if we should also be worrying about a customer's ability to give the game he's purchased to his brother.
If your goal is to maximize the number of individual copies sold, then I'd say go ahead and worry. I mean, I get where you're coming from. That said, bear in mind that consumers are used to being able to give away or lend their copy of a bit of intellectual property. "Sure, go ahead and borrow my [album/tape/CD/book/DVD/game]. MS attacked this by tying the software to your specific hardware setup, but I doubt that'd work too well for something that isn't an OS or a major software suite like MS Office.
I'm sure it'd be technically possible, but I'd figure you'll piss off and alienate your consumers. Stardock's approach seems to be to build consumer goodwill and capitalize on that. Their business model may be able to absorb more piracy, though, at the gain of not having to spend time developing a workaround or money licensing some godawful antipiracy software like SecuROM.
I think Steam manages to strike a decent balance by being a "softer" anti-piracy platform which has the dual benefit of allowing for wide-range distribution. Although I'd bet it comes with its own downsides as well (IE: how much do they take off the top for each sale?).
By the way, guys - piracy's a [word that is evidently a no-no, female doggie]. It's killing our ability to develop PC titles outside the MMO business model. We need something to make big-budget PC games fiscally attractive. But not at the price of alienating our customer base.
Best advice I can offer? Tell the suits to stuff it and make QUALITY games. Put the gameplay experience as a whole as your absolute priority. Above graphics, above this or that "must-have" feature. Focus on delivering as solid a gameplay experience as possible. If you guys are starting small, you'll have the benefit (possibly) of having an easier time with reviewers who will expect less from an indie gaming company than from an EA or an Activision.
Seriously, though, I cannot stress enough how much MORE the gameplay experience means to me over the "pretty" factor. Pretty wears off quickly. It's nice to have, but eye candy is like cotton candy. It looks impressive, but eventually you realize it's mostly non-substantive.
You want folks to buy big budget games, make them worthwhile in the consumer's eyes. Not the reviewers' eyes mind you. The CONSUMER'S eyes. Personally, I believe that consumers will go for a game that isn't QUITE as pretty as the latest "tech demo" whiz-bang graphics experience (IE: Crysis), and is more just a solid freakin' game that you want to play over and over and over.
Civ4 is not visually impressive these days. Not by comparison with marquee titles. It still has a rabid following, though, because of the gameplay. It's ALWAYS the gameplay, man.
@ Solo4114: Fair enough points, but not everyone taking part in this discussion lives in the USA. I'm not a lawyer but dealt with the relevant bits (consumer rights, EULAs, terms of service) as part of an economics/business studies degree, in the context of German law.
You won't see me claim I know much about the American legal system, but I'm fairly sure that generalisations by fiitting everything into rough analogies to established context like esemjay is fond of isn't appropriate for a legal context on either side of the pond (although it may be ok for discussing things like morality and fairness).
This thread really needs better differentiation between loose and formal points.
Good point, and I do sometimes forget that we're dealing with a series held in international acclaim.

Apologies for being quite so provincial.
On a per-case basis the secondary market actually hurts more than piracy: The person who bought a used game was obviously willing to part with money, which may not apply to the majority of pirates.
Yep. But consider the statement that person is making: the experience offered by this game is only worth $10-30. I do that ALL THE TIME. I think the Call of Duty games are uniformly worth about, oh, $20 a pop. That's my value judgment on the COD series. I find that most games do NOT deliver the level of entertainment out of the box that I expect for my $60, and even if one game in a series did, subsequent games often deliver a mediocre experience compared to the original. But hey, that's why I buy used games. If the gaming industry delivered more reliable, top-notch product, they'd get my $60.
The OP is specifically talking about transferring ownership of the account- which is, by definition, account sharing- and thus, pirating.
Minor point, but pirating is more accurately copyright infringement. Transferring software in breach of the EULA is not necessarily copyright infringement, and thus not necessarily piracy. Beach of contract which can lead to a termination of your Steam account, sure, but not piracy necessarily.