I think a lot of applications could and should update themselves, but users typically don't allow them. I think this goes back to a lack of trust that the applications won't destroy themselves or others. I recall a Symantec update that crashed our computer to the point that it required restaging. Though this is the extreme case, it really highlights the problem. One possible improvement is that an application could offer a path backwards. Greater trust could be earned if it offered a way to undo the damage that it might create. This wouldn't have helped the afore mentioned crash, but it might be a step in the right direction.