Very weird you don't know this: Even if you haven't heard of somebody who has paid for Whatsapp service (you must be surrounded of linux/opensource people), it already has sold millions of dollars. MILLIONS. *MILLIONS* (read it again).

It was the top selling application in several countries with revenues even bigger than Angry Birds! YES: PEOPLE PAID FOR IT.

There are 2 billion of Whatsapp messages PER DAY, Whatsapp Inc never reveals the number of users, but it must be like half of what Facebook has... I don't know a single person that uses Facebook and don't use Whatsapp. I actually know a lot of people (from work actually) who uses Whatsapp and will never have a Facebook page...

Just use Google. Example: http://www.ft.com/cms/s/2/30fd99a2-0...#axzz21W46XTT1

Actually now Whatsapp Inc has a newer strategy that might end without charging anymore: Whatsapp Inc is talking directly with the cell phone companies all around the world to include the software preinstalled in cell phones. Cell phone companies see Whatsapp as a boost of the data consumption, and doing so will really increase the data consumption. Why almost everybody uses Windows? because it's preinstalled in every PC out there. That's the strategy.

People think Whatsapp hurt the SMS traffic but that's not the case, since the great majority of cell phone users have low end cell phones, and just a few percentage use smartphones.

In conclusion, they don't need to sell your number to anyone. They are already millionaires.