Yes, we can't rule that. But we could clearly see that the Diaspora codebase screamed incompetence. Apple, on the other hand, has some very high quality products and decades of experience.
Yes, it is quite possible that this is a simple bug. The other option is also quite possible :)
It is equally possible that Apple is a giant conspiracy dedicated to concealing the grey aliens who actually control human civilization and are harvesting our brainwaves, which actually function as the raw compute for a giant intergalactic payments call center application, via Flappy Bird. Think about it.
That's not equally possible, due to Occam's razor:
http://en.wikipedia.org/wiki/Occam's_razor
Plus, the security services have a proven ability and intent. Be serious now.
Yes, it is quite possible that this is a simple bug. The other option is also quite possible :)