Would it damage to put out cigarettes on the chassis of aluminum mac books?
I would say that the only damage caused by a cigarette to the aluminum itself would be cosmetic.
Clearly, the pebbled surface will trap nicotine and ash on the Aluminum. I suspect that Apple anodizes their unibody parts - and if so, that creates a hard, durable layer of aluminum oxide that protects the metal from scratches, stains, and further oxidation
I also expect that action would drive most neat freaks up the proverbial wall, but from a chemical and heat aspect - a single lit cigarette doesn't have enough heat to do any damage. It would slightly warm up a small area of the case but do no harm to the insides. Also, I've seen solid aluminum ashtrays in use for tens of years in harsh environments with no real pitting or permanent damage to them. An internet search for "milled aluminum ashtray" or "milled aluminum engine block" will show that aluminum (and aluminum alloys) can stand up to substantial heat in diverse settings.
I would be more concerned at the smoke, tar, nicotine getting inside the display and the Mac, corroding the circuit boards, covering contacts in ports and clogging the blowers over time.
- Tacky, messy, provoke a reaction in others? - yes
- Damage the aluminum surface? - not so much
Yes, you can. But the aluminum surface will very likely be stained and contaminated due to the tar and ash getting lodged in the microscopic surface features. This may not be perceptible after an intense cleaning but a thorough cleaning might do actual damage to the surface. In all, this is a bad idea-- like cracking an egg on the hood of your car in the desert to prove that it will cook. Your paint job will never be the same until it is completely redone, and aluminum isn't removable the way paint is.
Can I put out a cigarette on aluminum Mac Books?
No, it is simply not possible. Apple only ever released Macbooks in plastic and polycarbonate models. While Apple did announce in October of 2008 an all aluminum MacBook model, the updated line of unibody MacBooks were rebranded as MacBook Pro on 8 June 2009 at Apple's 2009 Worldwide Developers Conference.