Some people might argue that piracy deprives a company of income, and therefore is stealing. Those people are liars, ignorant, or all of the above. Firstly, it is not actual income. It is only potential income. The difference between these is income is something what was definitely there, while potential income that could have been there. Because of this, something that only might have been there does not classify as a real object, and thus is not stealing. And we can say it is potential income and not real income by a series of questions.
Why do people pirate? Because they want something for free. So why do people buy software? Because it is better quality, and more likely to be safe. Thus bought software is safer than pirated software? Yes, as you never know if it's really Windows XP or Netsky, a devastating computer virus. So why do people pirate? Because they are not both willing and able to purchase the program/song/movie. If this is the case, were they likely to pay for the software anyway? Probably not.
This has highlighted that because they were not going to buy it anyway, it was not real income lost. Therefore it was only potential income lost, which goes back to it not being stealing.