Obama tried something similar for the Biden VP announcement in 2008, but word was leaked beforehand to mainstream media. Bottom line: social media are just not that important when it comes to VP announcements. But unlike in 2008, both Republicans as well as Democrats are now adept at using them.
Aside from the app, what does the Ryan do for the Romney ticket? It certainly humanizes the robotic Romney, who I've been saying since 2007 may be a Cylon. But, politically, it puts Romney hand-in-hand with the man who wants to undermine social security, and whose calls for cuts in government spending for the poor have been condemned by the US Council of Catholic Bishops - which is saying a lot, since Ryan is also an opponent of abortion.
I think this is a very good development for our political process - whether you're a progressive like me or otherwise - because it puts before us in this election some remarkably clear choices.