I will only download under 3 circumstances:
1. I own the game and it legitimately breaks. Since I don't own the game itself, but a licence to use the game I feel justified. The physical disc is just a medium. Also if the game gets stolen as well, since I paid for it. 
2. The game is unable to be aquired unless unreasonable steps are taken (out of print), I.E im not ebaying a game for $140 or one not available at all. Noone could possibly lose because noone cares enough to sell the game.
3. Its a free demo or released to the community.
However I will pay for a game again if the game has been say re-released for Vista. I paid for Prince of Persia the other day again even though I own it. It takes work to rework a game and they deserve the money I give them for it.
Also the instant I see a game released which I had considered unable to be aquired I would buy a licence to a legitimate copy.
3.
Tease.
