This is the exact reason that Lou Zocci created Gamescience way back in the early days of RPGs. Back then the only dice that were available were really crappy dice from China. These were the type included in the old D&D Red Box. Blue and brittle, they were my first dice. I remember the small flakes of plastic that fly off when they hit the table, changing the shape and balance (though they were made so poorly they barely had balance out of the box anyway). Gamescience was the first to make dice from high impact plastic and the first company (and it looks like one of the few) to care about balance. Here is an interview with Mr. Zocci himself talking about his dice:
An alternate method to test dice is using a mathematical method, like the chi-squared method (WARNING: MATH!).
You could also use these tests for evil, finding the dice that are unbalanced in your favor. Of course, we would never do that would we?