Originally posted by Zav If the rest of the lens is not weather resistant, is it really so useful?
Assuming it works, it can't hurt to have one less point of vulnerability that way. It obviously won't mean you can be indifferent to other spots where a camera or lens isn't weather-sealed, but it'd be handy enough for some of us. I don't own a single weathersealed lens and never have, but do enjoy not having to worry about the camera body itself. It means I can more or less treat the camera like a non-computerized one, and the lens mount would be the next biggest vulnerability there.
So no, it wouldn't make your lens weathersealed, but could be a lot better than nothing.