This made me stop to think.Lets assume you can control the dice roll, and that due to that and manufacturing defects that a given die is more likely to land with a given face up, if it starts with a different face up in your hand.If that were true, you'd almost have to mark a different face on each die, I mean what's the odds of all 4-6 die having the same favored side? Or even just having one of the <focus> or <hit> sides be the favored one?Now that I think about it, if someone had every die marked on a <focus> it would make it less likely that they were using that as a way to cheat.If the dice were randomly marked, no cause for concern.
If someone were to go with the old microwave the dice trick they'd have to be sure to mark a facing so they'd know where to start thier roll off from for maximum effectiveness.
I don't think an possible method for cheating would stem from manufacturing defects but more from a specific method of "soft" rolling which would require a specefic facing to get perdictible results from. I know and have seen people do it with 6 siders so I don't doubt it's possible with an 8 though likely less consistent.