Cell phones have become indispensable -- can you imagine not having one?

But can you guess how many people around the world now use cell phones? Do you want to even try?

Well, many more cell phones than jelly beans in that jar that we have always been asked to guess at school math night -- 2 billion to be exact, according to The McKinsey Quarterly, the online journal of the business consulting firm. With the world population approaching 6.5 billion (according to world and U.S. population clocks), that 2 billion figure is truly remarkable.

Let's see how long it takes Nokia, Motorola, Samsung, LG and all the other cell phone manufacturers to get a cell phone to everyone on earth. Anyone care to guess?