People often confuse any breach of a SLA as "piracy." That's not true.
Piracy is, at its foundation, the act of illegally copying software. However, in modern usage, it carries the connotation of distributing that copy in some manner. Most people who merely make two copies for storage at home would never be called a pirate by anyone, though technically he copied one more time than is legal.
Additionally, it's important to remember that SLAs are not gods. A contract of any kind, including an SLA, is only as legal as the courts uphold it to be. I once breached a tenant contract by failing to turn in a 30-day notice of leave, and they tried to bill me for another month. Needless to say, we took it to the lawyers and I won. Lawyer stated that in my home state in the US, it's illegal to have that kind of clause in a tenant contract. WIN
As for an SLA, they are rarely ever challenged in courts because most people chicken out of whatever they are doing as soon as they get a letter to quit, and most offenses are never prosecuted. However, it'd be nice to see more cases pop up and see how the SLA holds up in a court of law, especially in light of international laws that can complicate matters.
One fact is clear I believe: illegally copying licensed software and then selling it against the terms of the license is DEFINITELY both illegal and just plain wrong. You are actually earning a profit by robbing a company of its own product's sales. No way not to see that as criminal behavior, IMO.
As for the "I wouldn't buy it anyway so I just downloaded it for myself" argument, that's hard to evaluate. I think most everyone we know has used it, and most of the time it's probably true, since most "pirates" download software, try it out, don't like and/or need it and that's that. However, downloading Photoshop and using it day after day as your hobby or for your job definitely doesn't qualify as "wouldn't have bought it anyway." Yes, you would have. You are robbing the company of a genuine sale.
Let's note, however, that pirating software is not "stealing as if you're taking a DVD from the store." Why? Because you're not taking any DVD from a store. You're not taking any physical property, you're not removing a genuine item that could be sold from someone else's reach. By downloading, you create a new copy, and therefore have not "taken" anything in the traditional sense. Let's not use terms inappropriately just because we think it strengthens one argument.
However, no matter how we dock it up, it's still theft. If you obtain and make use of software without paying for it, it's theft by modern law according to pretty much all countries that recognize intellectual property law. In fact, there are even some international laws concerning that kind of theft.
Now granted, it's a bit hypocritical for us to breathe down someone's neck about it when we're installing OS X (any copy, legal or not) on non-Apple hardware, technically against the license agreement. But then again, that really couldn't be called theft.. could it? Has ANYONE ever been prosecuted for a breach of the SLA such as that? I'm using a legally purchased retail Leopard DVD, but apparently breaking the SLA by installing it on non-Apple hardware... what kind of crime does that constitute? If not a crime, is it merely a breach of contract? What is the listed penalty for this breach? If there is no penalty listed, which I couldn't find in the SLA, then how would any charges of any kind be levied?
Oh, and BTW, for those who are curious, the SLA says that it cannot be installed unless on "Apple-labeled" hardware. Well, here's my "Apple-labeled" hardware below:
BTW, here's a very interesting and short read PROVING that when SLA meets the courts, sometimes the SLA loses. Companies tried to screw customers over by using language like "you don't buy the software, you buy a license to use it." By wording it in such manners, it prevents you from being able to "sell" your copy because you don't own a copy, just a valid use-license which cannot be sold. This was deemed a violation of consumer rights and struck down, despite being part of numerous SLAs. Sticking it to the man in a good way!
From Wikipedia:Buying the original software. Licenses say that the buyer does not buy the software but instead pays for the right to use the software. In the US, the first-sale doctrine, Softman v. Adobe  and Novell, Inc. v. CPU Distrib., Inc. ruled that software sales are purchases, not licenses, and resale, including unbundling, is lawful regardless of a contractual prohibition. The reasoning in Softman v. Adobe suggests that resale of student licensed versions, provided they are accurately described as such, is also not infringing.