Whatsapp seems to have less revenue potential than products which have already shown an inability to find the black, such as AIM.
Edit: gonna try it
My city has 500,000 people. I'm going to estimate there are 500 liquor stores here. So that's 1 per 1,000 people. The USA has 330 million people, thus 330,000 liquor stores.
A liquor store is probably worth about $50,000. Thus, they are all worth $16.5 billion.
Whatsapp has 800 million MAU's. If 2% of them convert to $10 a month paying customers, that is $160 million per month.
They could run that business much cheaper than the current one, so say 50 employees at $10k a month each. $500k a month. Double that for hosting and rent etc. $1 million a month.
Those costs seem way too low in relation to revenue so let's just bump that up to 50% of revenue. $80 million/month.
So $80 million per month profit. Or over 2 liquor stores per hour, 24/7/365. In about 15 years they'd own every liquor store in America.