I was glad to see this question pop up on Reddit, because it's something I've often thought myself.  The artistic "cakes" (and I do believe the term deserves the use of "scare quotes") you see so often on television reality shows often seem more like constructions of plywood and Tinker Toys, covered with a bunch of fondant.

Don't get me wrong - these art cakes show a lot of truly impressive artistic skill.  But can you really call it a cake?  

I think my problem is that "meant to be eaten" is inextricably bound up with the word "cake" in my mind.  A cake that isn't meant to be eaten is like a car that isn't meant to be driven, or a plate that isn't meant to be eaten off of.  Oh wait, there are lots of those in the world!  After all, what is a Franklin Mint collectible but "a plate that isn't meant to be eaten off of"?

At any rate, a cake that is beautiful but not meant to be eaten - yes, I do sometimes have a problem with this.  However if you watch enough episodes of "Ace of Cakes" you will notice that there is an actual bakery in the front of the store, where they sell actual baked goods.  It doesn't come up very often, because most of the show takes place in the back room.

I have also heard that at most of these parties, the host will purchase two cakes - one art cake, and one "eating cake."  It's just that creating a big (yet delicious and beautiful) sheet cake does not make for very good television.  I suspect most of the "real cake" action ends up on the cutting room floor, which is a pity.

Buttercream frosting is what most of us would consider "the real deal."  It can be difficult to work with, but on the up side, it is delicious!  A basic buttercream frosting is one part fat (butter or shortening), and four parts powdered sugar.  Add a dash of vanilla for flavor, a tiny bit of milk to help the texture, and food coloring as needed.  Beat the butter and the sugar together until they make a nice creamy frosting.

You can vary the percentage of butter to sugar, depending on the effect you want to achieve.  The most radical variation I found online is this recipe, which calls for one cup of butter and six to eight (!) cups of powdered sugar.  But as you can see from the picture, this is for a "fluffy" icing similar to what you see on the cupcakes in the picture.

The trick to buttercream frosting is to maintain the temperature.  As many cake bakers have found to their dismay, if a buttercream frosted cake gets too warm, the frosting starts to run!  In drastic situations, the weight of the frosting running off the side of the cake can actually tear the cake in half down the middle.  (Doing a Google Image Search for "frosting disaster" can shed light on this problem.  Just remember that if you snicker at someone else's frosting disaster... don't come crying to me when karma strikes your cake down!)