Spot on again Grizzly.
Not to mention you dont want to give admin as you could end up getting rooted by them.
What i mean is they could dump a shell on your server and have access to / now that would be nasty.
Dont give anyone admin ever. Only a variant of it. A special usergroup if you must that gives them theme powers but no more.
Its worth protecting your ass here. I know far too many people that take advantage of such people.