What is a cloud? First, define a table (the furniture kind, that is)

I was listening to the excellent What is a Cloud from the Beginning podcast by John Willis and Michael Cote. I highly recommend listening to it. I like their style and they do justice to the topic. The intelligent discussion the two were having, as well as other "define cloud computing" discussions I've been involved in, reminds me of a mental trick my father likes to play on all his grandchildren. He asks them to define a table (the furniture kind, not the database kind). Invariably, the kids will start by saying that it is a square piece of wood supported by four legs or something of the sort. Then my father points out that it could be round, that it could be made of glass, that it could have one leg, or no legs at all. The clever kids then move from trying to define the physical characterisitics of a table to its functional characteristics. They say it's something that you eat off of. My father then points out that when we visit our bedouin friends in Israel we sit on a carpet on the floor and place the food plates on it and eat from it. Is that carpet a table? Of course not, the kids yell. They try hard various other angles, but to no avail.

The truth is there is no exact definition of what a table is. But what's equally true is that we all know a table when we see one. 

Cloud computing is similar. If you try and broaden the definition of clouds you end up with "the Internet". If you narrow the definition too much, you'll leave out a lot of things. I think that for the purpose of day-to-day conversations, we all know what we mean by cloud computing, how 'bout we leave it at that?