I don't disagree, but how would you implement this?
Results trump ideals every time.
Results trump ideals every time.
Moreover, when I last used Windows (XP, 2008), executables could still masquerading as .doc files. This would be easy enough to solve for MS, I think.
Which would be annoying. Users would either block it or ignore it.
> Of course, it should be easy opt out.
If it was easy enough, everyone would, rendering it useless.