Earlier quoted context omitted.
Moxie's argument is that interop takes place at the level of the operating system's notification tray. If you want to make a better WhatsApp, all you have to do is ... build a better app. The traditional obstacles are largely gone in the mobile world: • You can access the same social graph just by requesting the contacts permission on your mobile phone: it's not like Facebook where the social network is locked away.…
All those are true, but still iMessage is an important reason for many to pay more for an iPhone. So still it's pretty hard to create an attractive alternative, wouldn't you say ?
But then again in Europe iPhone market share is much lower.