I'm sure I'm in the minority but I don't consider ping a social network (nor do I Twitter, honestly). And that's just me. Twitter is so much more communication focused in my book where things like FB anf G+ have been more frivolous.
I never thought of Siri as search. To me it was more about interfacing with your device.
Is that what determines a flop, though? Siri is definitely known, and added value to the iphone and the apple brand overall. While I use Google Now and think it is superior, I'm not sure if performance would be enough to label Siri as a flop.