While I appreciate the desire to avoid dry leftover cake, a tube of extra frosting to cover the exposed surface could also work. I've never cared enough to think about it before.
I did read a book once called "How to cut a cake, and other mathematical conundrums" that described an algorithm for cutting a round cake into an arbitrary number of pieces, one per person, such that no one has a right to complain about the size of their piece. Basically you 1) make the initial cut 2) slowly move the knife like the hand of a clock from that point, until 3) any of the eaters says "cut," and you then you cut the piece there and give it to them and 4) return to step 2. If anyone thinks his or her piece is too big they could have said "cut" sooner. If they think their piece is too small then they must think someone else's piece is too big, which means while the too-big slice was being measured they could have said "cut" and gotten a larger piece.