You will proabably find that as you near the limit of the lens shift, the edge corresponding to the direction in which you are shifting starts to bend.
I.e. If you scroll the lens shift all the way to the bottom, the lower edge of the picture may well not be straight any more. (The corners will be lower than the middle.) If you scroll all the way to the left, the left edge of the image may no longer be straight.
I think this has something to do with projecting the image through the extremities of the lens. (Remembering my A-Level physics, I guess the further towards the edge of the lens you move the projected image, the more glass it as travelling through (as the angle of incidence to the glass decreases) therefore the more the effect of diffraction from the lens has on the light path. The corners nereast the shifted edge will be closest to the edge of the lens and hence effected the most by the diffraction.)
There should be no ELECTRONIC deterioration from using lens shift. This is a purely geometrical deterioration. I guess the answer would be to have a huge lens on the front of the projector. (please note, bigger lens does not mean more magnifiaction, thats due purely to the curvature) The huge lens would allow the image being moved behind it by the lens shift to remain away from the extremities.
It is a slight (I mean slight) issue with the Sony HS-50. I couldn't say whether the issue exists on other lens shifting projectors. Perhaps other owners can confirm or deny?!!