As of this post's writing, the world population is an estimated 6,499,923,849 people.
The article on Wired (linked above) also has an interesting commentary on how many people the Earth can actually support.
Here seems like a good place to insert one of my favorite Frank Zappa quotes:
The problem with the world is stupidity. Not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself?