You know... because they look like giant boogers.
Do your artificers suffer any side effects for working with crushed dragonshrds and incarnum or whatever magic dust you have them use ? The Cannith master maker has fluff of silvery hands from exposure. But what about the effects of ingestion? Can magic be a drug? Would kings/ nobles sprinkle it on food like gold leaf? What are some potential pluses and detriments for an addiction to magic dust?
I like to think of certain Arcane Materials as having varying affects for ingestion and overexposure.
Residuum could include a druglike effect when ingested, though it may also give you a stomach ache, or it may make you urinate Oozes for a week. Rather unpredictable, not something you want an addiction to.
Messing around with Incarnum may result in permanent alterations to one's Soul and self-awareness, some of the better cases may result in an incredible increase of self-esteem and some of the nastier cases may result in insanity (I never knew I was a frog before!) or death. Remember kids, don't mess around with the fundamental essence of your being.
I like the ideas of overexposure to Psionic Materials having the potential of altering one's mental state or giving Wilder talents.
A friend of mine pitched a character once that was addicted to residiuum. NIce idea but from paragon not quite a money drain anymore.
Depends entirely on whether or not the character gets used to it and needs more and more for the usual kick. After all, there is no basic cost to a unit of residium, so whether or not it is a money drain depends entirely on how much the character needs ;)