Security Checks in API functions

Do we really need them?

Xaraya makes heavy use of security checks, and since they result in 
performance hits we need ot try and reduce them where redundant or 
unnecessary.

API functions are always called by something else, so the idea presents 
itself: why not relegate security checking to whatever calls the API 
function in the first place?

Typical case of such calls is an update GUI function which does input 
checking and then delegates the actual update to an API function. The 
GUI function could just as easily do privilege checking, and often does 
anyway.

Of course there are exception cases, for instance API functions that 
create content for display, like the getmenulinks functions. There is 
also the question of what happens when one API function calls another, 
and so on.

Still, it seems to me that taking the removal of security checks as a 
starting point and then dealing with the exception situations as they 
present themselves may be a useful approach to reducing the number of 
unnecessary checks.

Opinions?

Marc