I'm not going to give a history of how drillium came about( frankly because I wasn't there to witness it), but it is my understanding that what was originally a way for the elite to save a few grams at the expense of durability became in itself a form of artistic expression. People could take components and customize the to their liking, possibly saving a couple (nearly inconsequential) grams in the process. Today we rarely see drilled/milled components being produced, but some manufacturers do make 'skeletonized' components (*cough* campy *cough*).
Drilling holes in critical bike components can lead to FAILURE OF THE COMPONENTS. I do not suggest doing this to your brake calipers (at first), stem, or handlebars or any other part of your bike for that matter. SERIOUS INJURY OR DEATH CAN RESULT FROM COMPONENTS FAILING. Seriously, if you're standing mashing the pedals, which is when parts are under the most stress, and the chainring lets go, you very well might faceplant into the handlebars and stem and crotch-plant on the toptube(ouch!). Or worse, lose control and veer into traffic. Please be careful if you choose to ride on drilled components!
That being said, it sure looks pretty when its done right!
and I've been commuting/riding mine for 3 months now with no issues.