Apparatenly, it's the "scientific" way to cut a cake to keep it fresh.  I'm not sure I'd try this on an 18" round though…

http://www.wcvb.com/news/yes-you-are-cutting-a-cake-all-wrong/26545720#!0xiXT

hold it together with an elastic band? he should stick to math ;)

Perhaps for a cake I was just preparing for my own (family) consumption.  No need to even try this for a cake that is going to be consumed the same day.

AThat could get pretty messy if your cake is covered in buttercream with no fondant!

For my own, in home, cakes, I often cut them this way.  I don't rubberband the halves together.  I just push them together [home cakes aren't on boards--just a plate] and cover with a cake dome.  I also do this with loaf items like banana bread.  No reason to do it with a cake that will be completely cut up and served in one go, though.

I think everyone who eats cake considers themselves to be an expert.   

A

My dad told us he used to do this when he was a kid...cut a slice straight across the middle, smooth the seam of fluffy frosting with a knife and make my grandmother think that she was either nuts or the cake was shrinking 

I vaguely recall seeing something like this. In an old Beetle Bailey strip. As I recall, Sarge, in defiance of a warning from Cookie, sneaked a slice of the General's cake, in the manner described, and in the final frame, the General noticed the odd elliptical shape of the cake.

this is absolutely perfect if you plan to eat your birthday cake all alone, in your empty flat, not even a cat to keep you company, AND you have a ton of rubberbands on hand, AND you have the patience to do all that fiddly cutting and turning.

i can tell you if i'm eating a cake by myself, i'm sticking a fork in the side and taking a bite...

Maybe 100 years ago, but hasn't this guy heard of gladwrap and airtight containers?  I mentally like my cake cut in to wedges (probably because you can have a bigger slice without looking like a guts) and triangle sandwiches.

It's hardly rocket science....  For years, I've been taking thin slices of pizza from my kids' plates before serving it at the table, doing something along these lines

I agree that the rubber band thing is yuk!  Why doesn't he just use clingfilm? 

AMakes sense. Although where they're taking that cake that it needs to be held together with the rubber band, I don't know.

Plus why was he cutting through the rubber band instead of, you know, just taking it off.

I think he did it as a joke, with us as the punchline.