Is Smoking Really That Bad For Audio Equipment?

I have my friends over periodically, and some of them smoke. At the moment, I ask them to go outside to have a cigarette because I'm concerned that smoke will be bad for stereo equipment. I don't worry much about the smell because I have hardwood floors and minimal furniture, so there's not much to trap the smell. Does cigarette smoke damage speakers or does it get into audio equipment and leave residue on electrical connections, etc? I am curious whether there have been any incidents where cigarette smoke actually harmed someone's equipment?