I am somewhat intrigued by this subject. When I first bought my E-m1, I had not thought that I should find weather sealing useful: I am not a fan of being outside in inclement weather, and in all the time that I had has an E-P3, I had no occasion to use such a feature (a plastic rain proof cover that I bought for it in 2012 being unused to thus day); yet I have found occasional use for weather sealing now that I have it: on a glacier in Iceland with constant rain, near the base of a large waterfall creating spray or in a (very short) downpour at a nature reserve. Even so, the usefulness seems a little marginal: in heavy rain or spray, the front element gets covered on droplets ruining photographs taken until it is cleaned, and in all but heavy rain, a non weather sealed camera can be stored under a jacket to emerge to take a photograph as necessary without injury. Despite this, weather sealed lenses seem very much to be in demand. When do people use this feature?