Originally posted by SPB I have a K10 presently and experienced exactly this problem after 1 week of ownership. It obviously does not affect my images, but every time I look through the viewfinder and see the speck of dust inside it annoys me. In my view this is a design fault.
They can't make cameras 100% dust proof. If you are using a zoom lens, you are probably pumping air around inside the mirror box every time you zoom. Every time you take the lens off the camera you are potentially getting dust inside.
Calling reality a design failure isn't realistic. Dust happens, dust has always happened, and photographers just have to learn how to deal with it.
Find something else to be annoyed about before you make yourself mental.