I spent a couple of years back working for a computer support company and saw some pretty badly smoke damaged computers. Things such as hard drives are particularly susceptible to smoke. A little smoke won't do much, true. However, 20 cigarettes a day in a small home office room can cause some serious damage. It doesn't help that when a computer user is smoking, they exhale *towards* the computer. It doesn't help either if that computer's a Mac that sits on top of the desktop.
Hard drives and fans are the most susceptible to smoke damage, in my experience. However, fan failure can, of course, also lead to overheating of other parts and cause indirect failure. This is especially true in a laptop where the fans are even more vital.
I never saw any smokers' laptops but I did see a fair few desktops with failed fans and hard drives. The fan failures in desktops meant that smokers tended to buy newer computers more frequently because of "it keeps crashing" style complaints (this was a tech support company so not warranty related) and the hard drive failures cost the users cash for new drives and cash for setting up their computers again. In fact, thinking about it, the company probably lost a fair bit of yearly revenue when the ban of smoking in workplaces came into effect a few years ago!
As far as smokers go, what bugs me the most is that they are oblivious to the damage that smoke can do. Oblivious to the damage to their health, the health of others, their hygiene, their youthfulness, their furniture, their houses resale values, their electronics. They're oblivious to all those yet get angry when any non smoker even suggests the damage's existence. "I don't smell", "smoking didn't make this laptop overheat", "my house isn't worth less, it doesn't stink at all".