Slightly off-topic, but here it goes:

I always get a bit annoyed when apps use the phone number as the primary identifier.

As somebody that just moved to another country, I now end up with a situation where I can either decide to lose my German whatsapp friends or not being discovered by my American whatsapp friends.

I would love to see the ability to get some sort of ID number and then being able to register more than 1 phone number with it.