One of the most common problems of camera equipment is moisture (especially when your camera equipment is not weather-sealed), as it may cause your equipment to malfunction.
The same goes for lenses as well. Because of moisture, our lenses end up getting those pesky fungi that are hard to remove. Paying for lens cleaning can be quite expensive, so you have to make sure yours are always in tip-top shape.
Check out my tips on how to prevent moisture from getting in your equipment.
(Photo by Kalyan Chakravarty via Flickr CreativeCommons)