How could Facebook integrate WhatsApp into their business?

How do you see Facebook potentially fitting WhatsApp in their ecosystem?

Do you think the market is too saturated for another startup?

The current players are WhatsApp, KIK, Viber, Google Voice, Google Hangouts.

Some ways Facebook could potentially make use of Whatsapp:

• Rebrand it into Facebook Messenger
• Monetize Whatsapp userbase with their ad platform
• Link Whatsapp accounts to Facebook accounts

But since they paid such a hefty price for it, the most likely scenario is that they'll let Whatsapp continue as is (as a separate platform).

Facebook perceives any app with scale that grabs people's attention span to be a threat. I'm quite certain that they're less concerned about making money off of Whatsapp and Instagram, as they are about self-preservation.