What a load of shit...
... mostly from non-smokers and the ever zealous ‘reformed’ smokers channeling their guilt and self-loathing into hatred of others. First of all, nicotine is not tar and to all intents and purposes isn't even present in the tar (we wouldn't bother smoking otherwise as the point is to breathe the smoke, extract the nicotine and exhale most of the rest). Secondly, the ash is a much bigger issue for computers and you have to smoke very heavily, very close to it and over extended periods to deposit significant amounts of it in the machine or else the machine has to be practically wind-tunnel like in its draw strength with a very cluttered interior or crap exhausting. Thirdly, the ash and assorted other rubbish is just the same as dust (more toxic, maybe even mildly radioactive if you have sensitive enough equipment but otherwise...) and the problems that occur with dust also occur with dust that is partly or mostly tobacco ash, I.E. this is absolutely routine.
I get that smoking smells horrible (it does to me, too and I smoke - hence I smoke outside and very occasionally in my car / van but always with the window full down and the fans on high to blow it clear of the interior) but you idiots are vastly overstating your case and aye, I have serviced many, many PCs including one belonging to an old mentor of mine who use to smoke unfiltered ‘Senior Service’ cigarettes at the rate of forty to sixty a day, and spent most of his day coding at the machine; the exterior was badly stained, there was about half an inch of ash and dust on surfaces that were horizontal when the PC was used and the fans were badly worn from pushing the extra weight around when spinning but there was no ‘gooey tar build up’ (get real folks, that doesn't come from cigarette smoke, it'll be vapourized fat or sugar) and some gentle directed air took it all off the board while a simple vaccum cleaner (remember those?) cleaned the case out. I didn't clean the exterior up, though, why bother?
Apple are probably stuffed on this, to be honest; it's not a biological hazard, it's not even a chemical hazard, really, and the warranty doesn't specifically exclude it, so I'd think it unlikely they succeed in court with an argument that smoking near the computer was the cause of the failure or that doing so was somehow an unusual or extreme environment. I also think the employee is on a hiding to nothing with the exposure claim.
As for mister “Smokers take death for granted” anyone who doesn't is in a for large, final and fatal surprise; death comes for you, too (barring some currently speculative medicine advances).