Dust - and far worse Smoke (nicotinic acid) - can cause a degredation of performance on computer systems. "Dust Bunnies" increase heat within a unit by minimizing proper air flow. Heat is one of the largest causes of hardware failure. Dust in the inner workings of a keyboard can make it almost useless. While severe airflow blockages can be caused by dust/dust bunnies within a computer thus causing heat problems - small amounts of dust are unlikely to cause problems unless they contribute to static buildup. The electrical charges caused by static CAN be enough (although may not be) to cause anything from small "crashes" to large scale hardware failure.. . Nicotinic Acid - mentioned above - is far worse than smoke. The Acid adheres to the board and reacts with the cross-channels. The effects are degraded performance, lack of stability, and general lack of servicablility. . . Many computer shops now charge a sur-charge to work on computers owned by folks that smoke around them, due to the health hazard of touching the components (nicotine through the skin).