Why not read the ToS? It's pretty clear and very user friendly. The short version - they don't store your data, and there is no right for Facebook to get that data historically.
That's not to say they can't change it in future, but I'm sure if they do there will be a massive exodus from the network.
And to further clarify on your comment - whatsapp is a paid for app, not advert supported. They only charge the iPhone users, however. Cost of the app is $1 for iPhone. Suspect android users would never touch it, as they don't have payment details set up on Google Play's store.
And it seems that they very rarely collect those fees, if at all. I've certainly had my android install over one year, and no request for payment. See plenty of other similar reports online.
Suspect getting users to pay $1 is going to be a real pain, not for the cost, but for the convenience factor.
"In the event that WhatsApp is acquired by or merged with a third party entity, we reserve the right to transfer or assign the information we have collected from our users as part of such merger, acquisition, sale, or other change of control." http://www.whatsapp.com/legal/
"The contents of messages that have been delivered by the WhatsApp Service are not copied, kept or archived by WhatsApp in the normal course of business."
followed by
"If the recipient is not online, the undelivered message is held in WhatsApp’s server until it can be delivered. If the message is undelivered for thirty (30) days, the undelivered message is deleted from our servers. Once a message has been delivered, it no longer resides on our servers. The contents of any delivered messages are not kept or retained by WhatsApp — the only records of the content of any delivered messages reside directly on the sender’s and recipient’s mobile devices (and which may be deleted at the user’s option)."
That's not to say they can't change it in future, but I'm sure if they do there will be a massive exodus from the network.
And to further clarify on your comment - whatsapp is a paid for app, not advert supported. They only charge the iPhone users, however. Cost of the app is $1 for iPhone. Suspect android users would never touch it, as they don't have payment details set up on Google Play's store.