How might WhatsApp change after being bought by Facebook?

There won't be ads, it will be the gateway drug to the larger Facebook network. Users will now need to create a FB account to use Whatsapp, potentially adding millions more users. (I know a lot of older folks who use Whatsapp to save money on SMS but not Facebook). It's a totally different entry point that just might bring them a formerly unreachable group of consumers. Facebook knows their product well enough, once a user invests a bit to create their network / journal / photo library, they tend to come back. I wouldn't mind if this means I can now answer whatsapp messenger on my Mac and iPad now as well.

One thing for sure is that the app will become slow. Just like the FB app on iOS. Rest of the things might be 1) fb login mandate (which I don't have , so screw it) 2) automated groups/friends pulled from FB profile. 3)  Plugins for shitty games from FB to work on whatsapp. 4) the transformation from a kool app to a sulking, time wasting, self approving sorry ass teenager website linked with Internet based messenger. Nothing for the better , a lot towards the gutter!

No ads at least. Not for a long time to come until Facebook pushes Whatsapp to be in the one-billion-users club. As mentioned in the official statement by Mark, they think the current revenue model (Which draws in about $5 million per year) is a great revenue model. Listen to the official statement here- http://www.shareholder.com/visitors/event/build3/stage/stage.cfm?mediaid=63337&mediauserid=0

I think they might put ads and link with facebook account option.

I guess they would let it remain as such as Yahoo has let Flickr and Google has let Instagram and Microsoft has let Skype. For me, it is a potential competition murder by FB because Whatsapp was threatening it big time.

In my point of view, facebook will never change any of the whatsapp existing features. The only thing could be installing a feature that allows you to pull FB contacts into whatsapp.

I don't think FB will change any of the features of Whatsapp! FB never actually changes the core of any application. For example, Instagram! Features that can be added are: Sync  FB contacts with Whatsapp contacts so that you don't need to open  Facebook every time you need to message any of your "FB" friends. You  can message them through Whatsapp. One nice feature they can add is if any one messages us on FB, it should be delivered on Whatsapp :) One  main concern is the user privacy. This privacy breach will be an issue  as FB will definitely use our personal data to boost their sales and  businesses. P.S. Sorry for grammatical mistakes. Let me know if  there are any. I am new to Quora and wanna improve my English writing  skills. :)