If I go out and pirate Spore instead of buying it, I just decreased their sales. I stole it instead of buying it.
Now if you want to argue that the people pirating would never have bought the game, then file. It doesn't decrease sales in that respect. It is, however, still illegal. If the game companies don't do anything about it, then the government should.
It can only be counted as a lost sale if the potential was there, but the simple fact of the matter is that piracy almost never kills the potential. People who pirate things do so because they don't have the money to go out and buy them. In fact, most pirates live in countries where the average person makes less than $20 a day, and legitimately buying a game in those countries costs you twice as much (nominally) as it would in the US (which means, considering purchasing power, it is 20 times more expensive).
You can't squeeze water out of a rock, and when these companies start trying to fight piracy that's what they are hoping to do. They want payment from people who just don't have it. Notice how Ubisoft is also using this system of theirs to prevent used sales - they want to squeeze more money out of people for themselves, even at the expense of people who legitimately buy products but can only afford them second-hand. Again, they are trying to get money from people that just don't have it to give.
That aside, piracy is only illegal some places. Even in rather wealthy countries like Sweeden, piracy is acceptable, and in poorer ones it's simply a way of life. The companies that try to fight piracy are trying to fight human nature, and that never, ever works out well. In this case, they are spending a ton of money for something that will be undone for free by any number of people and mistreating their legitimate customers at the same time. It's little wonder that basically no one outside of Nintendo is making money on video games.
You do not have the right to never be offended.