Why would messaging be a winner-take-all market? I mean, it's just pushing around a bunch of bytes. Shouldn't be too difficult to specify.
And the carriers charged 20 cents per SMS [1]? Yup, I remember those days. No thanks.
[1] http://gizmodo.com/5832245/atts-new-text-plan-overcharges-yo...
(I'm not going to switch to the 2nd best app where I can only reach 10% of my friends.)
There is no reason why the social network of mankind should remain captured in the userbase of a single messaging app. And it is the abstract social network that does provide the network effects.
Funny enough, they also fail to see that forcing people to adopt something doesn't work either. For a company that lives off advertising, they sure don't show much skill at marketing.
Would I be required to install a new app for checking an additional inbox?
It'd probably have to be a system where the server must verify that the number actually belongs to you by sending you a "traditional" SMS with an access code. You'd also need a trust network among the servers or else there would be servers announcing every telephone number out there as theirs.
Regarding the app, I guess any app that supports the protocol would do, even ones that also do other things. This should produce a healty app ecosystem.