Most Dice Aren't That Random
Dice aren’t just dice. And you don’t need to consciously cheat to have dice that are quite a bit less than random; which Colonel Zocchi ain’t afraid to tell you:
For a more scientific study of the imprecision of dice, check out this paper, not to mention the Dice-o-Matic. Now if you’ll excuse me, I just checked my own dice, and they’re… questionable, so I’m off to find a place to buy casino-grade dice in Copenhagen; if not, Game Science it is.
PS: If you, like me, like playing around with various dice probabilities for use in for instance a roleplaying system, AnyDice Calculator is your best friend in the whole world. And if you need insta-dice on-the-go, check out Mach Dice for the iPhone.