If you download a game you otherwise would have bought, that is directly taking money from the developers. If you download a game you otherwise would not have or could not have bought, then the developers dont really lose anything.
But by downloading that game, you could potentially be persuaded to buy future installments of that game, or other projects from that studio from being shown how great their work is. In which case the Studio would benefit from your piracy.
Though I think they just need to make a workable renting service for PC games, where you download it and can play it for up to X hours, then pay more to add more time. This would drastically cut down the cost of entry into the game, bringing in more players; and if the game is good enough they will pay for more time and could then have the option to pay the remainder of the full retail price and own the game. Allowing the consumer a cheap way to try games before committing to the full retail price.
I am sure someone can come up with a way to limit the amount of time someone can play a game, and implement that to allow for online rentals. And with 50mbps internet connections, soon 100mbps where I am downloading a full game can take less then 20min (16min for me with BFBC2! go EA and COMCAST!).
Online Piracy will not end until there is a price effective and convenient service to compete with it.
I knew tons of people who used to pirate music, now all of them either buy it from Itunes, or have a Rhapsody or Napster subscription. Napster at $7 a month provides such convenience and low price that it there is no compelling reason not to pay for your music.
This can be the same with PC gaming too. Downloadable Rent to Own can kill PC game piracy!