Grand Theft Auto: San Andreas and Halo 2 were two really big blockbusters to hit the stores just recently, and (surprise, surprise) they were available on the net to download even before release. With the spread of broadband, games piracy is getting easier and easier these days. Whether or not this actually impacts sales is one thing, that it concerns games companies greatly is another. Games development companies hate this kind of piracy, and want to see it stamped out.
Which is exactly how Valve feel about Half Life 2 - they don't want it pirated at all. Their solution? Give everyone in the world the game at the same time; US, UK, Italy, China, France, Germany - they all get localised versions on the same day. This stops a release into one region being leaked illegally into another, because the game is available in all regions at once. Valve seem to understand what a lot of other companies do not, that staggered worldwide releases aren't conducive to their anti-piracy cause. To enforce this further, Valve have built into the game a an online authorisation system which means that no-one can play the game until Valve has hit an online switch that says the time is right. One wonders if these sorts of moves will become the norm before too long. More here.