Pry these sparkle dice from my hands at your own peril, villain!
Let's say your elf was stabbing a mean little orc and you had to roll d6 for damage. I hand you a d7 with two "1"s on it (i.e. 1,1,2,3,4,5,6). Would you be cool with that?
Apparently a lot of roleplayers would be totally cool with this.
Indeed, this is the magnitude of inaccuracy in cheap d6s, according to this 2006 study based on 144,000 dice rolls using replicates of dice from different manufacturers. Both Chessex and Games Workshop dice showed this level of inaccuracy - actually a bit worse than this, on average.
Trivial? Insignificant? Meaningless given the small number of rolls in a session? Ummm. Not really...
The study I cite has been discussed endlessly in the various gaming forums over the last several years, yet most roleplayers still don't seem to care in the least that their dice might be way way off. I find the psychology here to be very interesting and quite different from the other gaming subcultures I've crossed paths with.
I spent some years playing Magic: The Gathering and, later, strategy boardgames. In Magic I could not conceive of any player ever being okay with slipping a fifth replicate of a card into a deck (you're only allowed four). In boardgaming, likewise I could scarcely imagine a player showing up to a game of Settlers of Catan or Stone Age with their own funky dice for their own personal use. This would immediately create suspicion amongst the other players, whether it was at a tournament or a dining room table. So why is this okay in roleplaying games?
It's fascinating to read the viewpoints of the dice inaccuracy apologists who responded to my previous post, or this spin-off discussion at RPGSite. A lot of people are quite open about how they are more concerned about the color of their dice - the way they sparkle in the fluorescent basement light or the way they glisten when coated in Cheeto grease - than how they function. One player used the RPGSite thread as a chance to show off a picture of the heavily worn early-80s TSR dice he stills plays with. Obviously these dice have significant nostalgic value to this person, which I can totally understand. I don't think this person would ever argue that his dice roll accurately, however.
Ultimately it turns out that many roleplayers value aesthetics over function when it comes to dice. Dice are symbols, "potent totems of gamer culture" as S. John Ross puts it, that players use to communicate aspects of their identities. The person with the dirty old Dragon Dice is old school... the person with the sparkle dice is a fancy-pants... the person with the 100 cheapies is well-prepared... the person with the sack of 23 weird dice is superstitious. And so on.
Upon reflection, I actually think this is kind of cool and is part of what makes the RPG world such a fun and interesting place. I love gaming with oddball eccentrics, including people that speak in funny voices and wear felt elf hats. Of course a lot of these kinds of folks are going to have complex emotional relationships with their dice. You know what? It's fine with me... For the record, I have never discussed dice accuracy at a game session, much less asked somebody not to use their personal dice. I welcome players to bring and use their special juju dice - this is a charming and idiosyncratic roleplaying tradition that I do not wish to change. I value the cultural weirdness of dice traditions more than I am concerned about a given players' roll outcome accuracy.
On the other hand, I can think of no reasonable excuse for why a DM should not make an effort to use accurate dice. I am of the traditional view that a DM should strive to be an impartial referee, and this would include allowing players to expect fair dice rolls. I would be interested in hearing a rational argument for why a DM shouldn't invest $5-10 in a set of good dice.