I'm assuming you are talking about the Web Services API. The main issue with that system by default is that everything is done by the items ID. Unfortunately I don't have access to our installation or database and to accomplish using the ID's of users, courses, etc... I would have to store all that in a local database when I create it, which my institution will not allow me to do.
I have created some API functions that will get items by the shortname or usernames but as above I can't add it to my installation or else this wouldn't be that big of a deal.
My only hope right now is for what I have proposed to be added to the core until I can ever get access.