Gamasutra has put together a summary of the panel discussion that Blizzard's Rob Pardo gave this week during the Game Developers Conference. The topic was the company's "core design concepts", which one could argue are the best in the industry despite not really being that revolutionary:
As designers, say Pardo, there is a natural tendency to worry about punishing the player rather than rewarding them, but a clever designer can play with a player's psychology and turn it into a bonus.
Pardo related an example of World of Warcraft's rest system: when the game launched, players were punished for playing too long by having their experience gain percentage drop from 100 to 50 percent after a couple hours of play.
"Beta players universally hated this idea and were screaming bloody murder," said Pardo.
The fix? Turning this into a bonus scenario instead. Players now start at 200 percent experience and drop down to 100 percent. It's the exact same mechanic, but now it's a bonus instead of a punishment.