>It pains me endlessly that I must know whether I can contact person X via iMessage or WhatsApp or now this.

I think the situation is short term though (5 years?). Right now there's a battle for dominance on the mobile front and everyone is taking the proprietary route in an attempt to gain market dominance.

AOL had this chance with standardization years ago with AIM but they not only screwed up the entire company but this product as well.